ArticleLiterature Review

Salvinorin A and Related Compounds as Therapeutic Drugs for Psychostimulant-Related Disorders

Authors:
  • Ribeirão Preto Medical School, University of São Paulo, Brazil
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Abstract

Pharmacological treatments are available for alcohol, nicotine, and opioid dependence, and several drugs for cannabis-related disorders are currently under investigation. On the other hand, psychostimulant abuse and dependence lacks pharmacological treatment. Mesolimbic dopaminergic neurons mediate the motivation to use drugs and drug-induced euphoria, and psychostimulants (cocaine, amphetamine, and methamphetamine) produce their effects in these neurons, which may be modulated by the opioid system. Salvinorin A is a κ-opioid receptor agonist extracted from Salvia divinorum, a hallucinogenic plant used in magico-ritual contexts by Mazateca Indians in México. Salvinorin A and its analogues have demonstrated anti-addiction effects in animal models using psychostimulants by attenuating dopamine release, sensitization, and other neurochemical and behavioral alterations associated with acute and prolonged administration of these drugs. The objective of the present article is to present an overview of the preclinical evidence suggesting anti-addictive effects of salvinorin A and its analogues.

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... This practice is common especially in young people and adolescents with the goal of reaching a psychoactive state and experiencing powerful hallucinations (Casselman et al. 2014;. Effects begin rapidly and include visual hallucinations and motor effects (dos Santos et al. 2014;Hooker et al. 2008). Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). ...
... Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. ...
... Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. Generally, after 15 to 30 minutes of consumption via smoking the effects disappear; however, there are reports of prolonged effects up to approximately 1 hour (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). ...
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Salvia spp. are a genus of herbaceous plants characterized by woody stems and lanceolate leaves grouped in spikes of bluish-purple leaves with wavy margins. The salvia species most commonly used as additives in animal diets are: Salvia lavandulifolia, Salvia officinalis and Salvia hispanica. One species of particular interest for livestock nutrition is Salvia hispanica, for which favorable results for average daily gain have been observed at dietary inclusion rates of 1-40% in species as varied as rabbits, goats, chickens, lambs, cattle, and quail. In rabbits, Salvia hispanica isadded to diets with the goal of improving vascular function in hypercholesterolemic conditions. Common commercial rabbit diets can raise cholesterol levels, while Salvia hispanica increases levels of triacylglycerol and alpha linoleic acids, the latter of which are involved in improved vascular function. Addition of Salvia hispanica additionally alters fat partitioning and storage in rabbits, improving meat quality. Supplementation of diets with Salvia hispanica contributes to improved efficiency and improved economic gains for small producers, thereby improving the sustainability of rabbit production. The use of natural herbs such as Salvia spp. also allows for improved productivity in a manner perceived by consumers and regulatory agencies to be more “natural” than synthetic growth promoters. The objective of this review is therefore to demonstrate the benefits of the addition of Salvia spp. to commercial rabbit diets.
... This practice is common especially in young people and adolescents with the goal of reaching a psychoactive state and experiencing powerful hallucinations (Casselman et al. 2014;. Effects begin rapidly and include visual hallucinations and motor effects (dos Santos et al. 2014;Hooker et al. 2008). Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). ...
... Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. ...
... Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. Generally, after 15 to 30 minutes of consumption via smoking the effects disappear; however, there are reports of prolonged effects up to approximately 1 hour (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). ...
Chapter
Salvia spp. are a genus of herbaceous plants characterized by woody stems and lanceolate leaves grouped in spikes of bluish-purple leaves with wavy margins. The salvia species most commonly used as additives in animal diets are: Salvia lavandulifolia, Salvia officinalis and Salvia hispanica. One species of particular interest for livestock nutrition is Salvia hispanica, for which favorable results for average daily gain have been observed at dietary inclusion rates of 1-40% in species as varied as rabbits, goats, chickens, lambs, cattle, and quail. In rabbits, Salvia hispanica is added to diets with the goal of improving vascular function in hypercholesterolemic conditions. Common commercial rabbit diets can raise cholesterol levels, while Salvia hispanica increases levels of triacylglycerol and alpha linoleic acids, the latter of which are involved in improved vascular function. Addition of Salvia hispanica additionally alters fat partitioning and storage in rabbits, improving meat quality. Supplementation of diets with Salvia hispanica contributes to improved efficiency and improved economic gains for small producers, thereby improving the sustainability of rabbit production. The use of natural herbs such as Salvia spp. also allows for improved productivity in a manner perceived by consumers and regulatory agencies to be more “natural” than synthetic growth promoters. The objective of this review is therefore to demonstrate the benefits of the addition of Salvia spp. to commercial rabbit diets.
... This practice is common especially in young people and adolescents with the goal of reaching a psychoactive state and experiencing powerful hallucinations (Casselman et al. 2014;. Effects begin rapidly and include visual hallucinations and motor effects (dos Santos et al. 2014;Hooker et al. 2008). Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). ...
... Each Salvia divinorum leaf has between 0.25 and 0.75 g of salvinorin A (European Monitoring Centre for Drugs and Drug Addiction 2015). Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. ...
... Doses between 200 µg and 500 µg are estimated to be necessary for the effects to be produced, and the dose of salvinorin A that reaches the brain is less than 10 µg (Zawilska and Wojcieszak 2013;Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). Regarding the duration of effects, the action of salvinorin A is estimated to be short, effects generally manifest within 5 minutes and reach the peak after 10 minutes of consumption (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014;. Generally, after 15 to 30 minutes of consumption via smoking the effects disappear; however, there are reports of prolonged effects up to approximately 1 hour (Cunningham, Rothman, and Prisinzano 2011;dos Santos et al. 2014). ...
Chapter
Salvia divinorum is a plant of the genus Salvia that belongs to the family of mint Lamiaceae which grows mainly in Oaxaca - Mexico in very humid environments and rich soils. S. divinorum is usually known as “Ska Pastora” or “Ska Maria Pastora”, having more common names among the youth community as “magic mint”, “Diviner’s Sage”, “Sally D” or “Purple Sticky”. Until the mid-60s, knowledge of this genus/family was restricted to an indigenous group located northeast of Oaxaca in Mexico, the Mazatecs, who used it for several centuries during their divine ceremonies, healing processes and in the training of healers. Some studies carried out with S. divinorum and its bioactive compound (salvinorin A), showed that it has effects with potential interest for human therapy, such as in the treatment of drug dependence, pain, neurological, gastrointestinal diseases and as anti-inflammatory drug. However, in the last years it has been consumed as a recreational drug of abuse due to its psychoactive proprieties. Both S. divinorum and salvinorin A have become controlled drugs in several countries, but they are not listed in the Schedules of the United Nations Drug Conventions. This chapter will aim to perform a critical review about Salvia divinorum and its components, modes of consumption, effects, interactions, therapeutic uses, their determination in biological specimens and laboratory difficulties; other toxicological aspects will be discussed as well. Keywords: Salvia divinorum, salvinorin A, effects, therapeutic uses, toxicological aspects
... An interdisciplinary group of professionals led by psychologist Sacha Domenech founded in 2001 the civil association Runa Wasi (http://runawasi.blogspot.pe/), in Buenos Aires, Argentina. The initiative follows the experience of the community Ayllu Tinkuy created in the 90s by Domenech (1996), who has been trained as socio-therapeutic operator in therapeutic communities by the "Progetto Uomo", and as practitioner of traditional Peruvian medicine. ...
... Currently, it is possible to find in the scientific literature pre-clinical evidences suggesting anti-addictive effects of S. divinorum at pharmacological level (dos Santos et al., 2014). Salvinorin A, opioid receptor agonist extracted from S. divinorum, has been identified as a potential therapy for drug abuse and addiction, having demonstrated anti-addiction effects by attenuating dopamine release and dopaminergic activation, sensitization, and other neurochemical and behavioral alterations associated with acute and prolonged self-administration of addictive drugs (Kivell et al., 2014). ...
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Objective. This article aims to give an overview of the major American centers using traditional herbal medicine or their derivatives in the treatment of substance dependence. Methodology. For the purpose of this article we have considered a small number of plants hailing from South, Central and North America. The research has been based on scientific literature, information exchange with treatment centers, internet searches and the personal experience of the authors. Results and discussion. Results show the relevance of certain psychoactive plants well known also for inducing modified states of consciousness (MSCs) including Ayahuasca, Coca, Wachuma, Tobacco, Psilocybe mushrooms, Salvia divinorum and Peyote. Conclusions. Plant based assisted therapy for the treatment of substance use disorders appear to be a promising field of research, although validation of the clinical outcomes need to be improved for the majority of the analyzed cases.
... Antagonism of the NMDA receptor is shared with the anesthetic hallucinogen ketamine, which has been reported to show anxiolytic (Kolp et al., 2007), antidepressive (Luckenbaugh et al., 2014;Sos et al., 2013), and antiaddictive (Dakwar, Levin, Foltin, Nunes, & Hart, 2014;Krupitsky et al., 2007) effects. Agonism of the κ-opioid receptor is shared with the plant hallucinogen salvinorin A, which has potential effects in the treatment of stimulant-related disorders (Dos Santos, Crippa, Machado-de-Sousa, & Hallak, 2014). Agonism of the 5-HT 2A receptor is shared with classic serotonergic hallucinogens such as LSD, psilocybin, and ayahuasca/DMT, which has anxiolytic, antidepressive, and antiaddictive properties Dos Santos, Osório, Crippa, Riba, et al., 2016;Nunes et al., 2016). ...
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Background and aims: Ibogaine is a naturally occurring hallucinogenic alkaloid with a therapeutic potential for reducing drug craving and withdrawal. To the best of our knowledge, no systematic review was previously performed assessing these effects. Thus, we conducted a systematic literature review of human studies assessing the antiaddictive effects of ibogaine. Methods: Papers published up to July 2, 2016 were included from PubMed, LILACS, and SciELO databases following a comprehensive search strategy and a pre-determined set of criteria for article selection. Results: Two hundred and fifty-nine studies were identified, of which eight met the established criteria. Seven studies were open-label case series with ibogaine and one study was a randomized, placebo-controlled clinical trial with noribogaine. Case series suggest that a single dose or a few treatments with ibogaine may significantly reduce drug withdrawal, craving, and self-administration in dependent individuals lasting from 24 h to weeks or months. No significant effects of noribogaine on opiate/opioid withdrawal were observed in the clinical trial. Conclusions: Considering the necessity of new drugs that may produce fast-acting and sustained effects in opiate/opioid and cocaine dependence, the potential beneficial effects of ibogaine/noribogaine should be further investigated in controlled trials.
... Although salvinorin A has apparent selectivity for KORs, it has negligible affinity for other known receptors including the μ-, δ-, and ORL-opioid receptors, the CB-1 and CB-2 cannabinoid receptors, the muscarinic and nicotinic cholinergic receptors, serotonin receptors (including the 5-HT2A receptors, the site of action of LSD), and various ionotropic and metabotropic glutamate receptors ( Roth et al., 2002;Chavkin et al., 2004;Roth et al., 2004). Because salvinorin A has agonistic activity on KOR, it possess many different properties such as effects on behavioral and neurobiological endpoints, effects on KOR/dynorphin system during stress, or in addictive states, neuroendocrine effects, and its effects for the treatment of neuropsychiatric diseases ( Butelman and Kreek, 2015;dos Santos et al., 2014). Effects on mood, depression, and neuropsychiatric disorders are among the most important activities of salvinorin A, which is mostly dominated through κopioid antagonism. ...
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The genus Salvia, from the Lamiaceae family, has diverse biological properties that are primarily attributable to their diterpene contents. There is no comprehensive review on the molecular signaling pathways of these active components. In this review, we investigated the molecular targets of bioactive Salvia diterpenes responsible for the treatment of nervous and cardiovascular diseases. The effects on different pathways, including apoptosis signaling, oxidative stress phenomena, the accumulation of amyloid beta plaques, and tau phosphorylation, have all been considered to be mechanisms of the anti-Alzheimer properties of Salvia diterpenes. Additionally, effects on the benzodiazepine and kappa opioid receptors and neuroprotective effects are noted as neuropharmacological properties of Salvia diterpenes, including tanshinone IIA, salvinorin A, cryptotanshinone, and miltirone. Tanshinone IIA, as the primary diterpene of Salvia miltiorrhiza, has beneficial activities in heart diseases because of its ability to scavenge free radicals and its effects on transcription factors, such as nuclear transcription factor-kappa B (NF-κB) and the mitogen-activated protein kinases (MAPKs). Additionally, tanshinone IIA has also been proposed to have cardioprotective properties including antiarrhythmic activities and effects on myocardial infarction. With respect to the potential therapeutic effects of Salvia diterpenes, comprehensive clinical trials are warranted to evaluate these valuable molecules as lead compounds. Copyright © 2016 John Wiley & Sons, Ltd.
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Salvia divinorum is a medicinal and psychoactive plant endemic to the Sierra Madre Oriental of Oaxaca, Mexico. The Mazatec people have been using the leaves for centuries in ceremonies for its psychoactive properties and as a treatment for arthritis and inflammation, gastrointestinal problems, headaches, and addictions, among other uses. The active principle of Salvia divinorum, the terpene salvinorin A, is a uniquely potent and highly selective kappa-opioid receptor agonist and, as such, has enormous potential for the development of valuable medications. Among them, the most promising include safe and nonaddictive analgesics, neuroprotectors, short-acting anesthetics that do not depress respiration, antidepressants, anti-inflammatories, medications for the treatment of addiction to stimulants and alcohol, and drugs to treat disorders characterized by alterations in perception. The Mazatec consider Salvia divinorum to be a very powerful plant spirit that should be treated with utmost respect, and the preparation for the ceremony requires a strict regimen. They chew the fresh leaves at night while chanting and praying. In the Western use, the dry leaves are potentiated in extracts to be smoked. A lack of information about the appropriate doses and other considerations while smoking the extracts could result in overwhelming experiences due to the high potency and fast onset of the substance. For the Mazatec, smoking the plant is not the preferred mode. How could we create a bridge between the two perspectives? In this chapter, I will try to clarify the best ways to use Salvia divinorum for medicinal, psychotherapeutic, and inner exploration purposes.
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Salvia divinorum is a member of the Lamiaceae family and contains the psychotropic diterpene and kappa-opioid receptor agonist salvinorin-A. Originally a shamanic inebriant used by the Mexican Mazatec Indians, the plant and its preparations are becoming increasingly popular among non-traditional users. Demographic data and information on pattern of use and subjective effects were obtained by means of self-report questionnaires from a sample of 32 recreational users of salvia and other psychedelics. Involvement with salvia appeared to be a recent phenomenon. Smoking the extract was the preferred form of administration. Subjective effects were described as intense but short-lived, appearing in less than 1 min and lasting 15 min or less. They included psychedelic-like changes in visual perception, mood and somatic sensations, and importantly, a highly modified perception of external reality and the self, leading to a decreased ability to interact with oneself or with one's surroundings. Although some aspects of the subjective effects reported were similar to high doses of classical psychedelics with serotonin-2A receptor agonist activity, the intense derealization and impairment reported appear to be a characteristic of salvia. The observed simultaneous high scores on the LSD and PCAG subscales of the Addiction Research Center Inventory (ARCI) have been previously reported for other kappa-opioid agonists, and support kappa receptor activation as the probable pharmacologic mechanism underlying the modified state of awareness induced by salvia.
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Salvinorin A (SA) is a highly selective kappa opioid receptor agonist and the putative psychoactive compound in Salvia divinorum (SD), an increasingly abused hallucinogenic plant. The objectives of this study were to characterize the physiological and subjective effects of SA versus placebo and measure drug and metabolite levels. Sublingual SA doses up to 4 mg were administered in dimethyl sulfoxide/polyethylene glycol 400 solution to eight SD-experienced subjects using a placebo-controlled ascending-dose design. No dose of SA produced significantly greater physiological or subjective effects than placebo. Furthermore, effects did not resemble reported "typical" effects of smoked SD. SA was detectable in plasma and urine, but was, in most cases, below the reliable limit of quantification (0.5 ng/mL). Our results suggest that the sublingual bioavailability of SA is low. Higher doses, alternate formulations, or alternate routes of administration will be necessary to study the effects of SA in humans.
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kappa-Opioid agonists may functionally antagonize some behavioral effects of cocaine, but the role of mixed kappa/mu receptor activity is unclear. The effects of three mixed kappa/mu agonists (MCL-101, (-)cyclorphan, and Mr2034) and one kappa-selective agonist (enadoline) on cocaine self-administration and cocaine discrimination were compared in rhesus monkeys. Acute treatment with all kappa agonists dose dependently reduced cocaine-maintained responding and produced a downward shift in the cocaine self-administration dose-effect curve (0.001-0.32 mg/kg/inj, i.v.). During 7 days of chronic treatment, (-)cyclorphan (0.0032-0.032 mg/kg/h) and MCL-101 (0.0032-0.032 mg/kg/h) each dose dependently reduced cocaine self-administration maintained by a dose near the peak of the cocaine self-administration dose-effect curve. MCL-101 (0.032 mg/kg/h) produced selective and sustained decreases in cocaine self-administration, whereas (-)cyclorphan (0.032 mg/kg/h) had selective but transient effects. In addition, these mixed kappa/mu agonists produced fewer side effects (some salivation) than the kappa-selective agonist (sedation, salivation, emesis). However, none of these kappa agonists substituted for or antagonized cocaine's discriminative stimulus effects in monkeys trained to discriminate cocaine (0.4 mg/kg, i.m.) from saline. Thus, kappa and mixed kappa/mu-opioid agonists may reduce cocaine self-administration without altering cocaine's discriminative stimulus effects. Mixed kappa/mu agonists appear to offer some advantages over selective kappa agonists as potential treatments for cocaine abuse.
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Drugs can function as punishers. However, work on the study of drugs as punishers is limited, as is the range of compounds known to function as punishers. Kappa opioid agonists, which have received much experimental attention as potential therapeutics for drug abuse, reportedly produce aversive effects. However, kappa agonists have yet to be tested as punishers of behavior. The goal of the current study was to determine if a kappa agonist could function as a punisher of drug self-administration. In separate experiments, monkeys were allowed to choose in a two-lever choice design between intravenous injections of equal doses of either cocaine (0.1 mg/kg/injection on each lever) or remifentanil (0.1 μg/kg/injection on each lever) when one of the two options was mixed with various doses of the kappa agonist, salvinorin A. Choice for the cocaine and remifentanil options that were combined with salvinorin A decreased as a function of salvinorin A dose in all monkeys. However, operant response rates were not systematically affected by salvinorin A administration. The present findings demonstrate that the kappa agonist, salvinorin A, can punish self-administration of a psychotimulant, cocaine, and a mu opioid, remifentanil. In consideration of these findings, it may be possible to curtail the abuse of some drugs by contingently delivering kappa agonists (e.g., as combination formularies for prescription medications).
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Salvia divinorum is a sage endemic to a small region of Mexico and has been traditionally used by the Mazatec Indians for divination and spiritual healing. Recently, it has gained increased popularity as a recreational drug, used by adolescents and young adults as an alternative to marijuana and LSD. Salvinorin A, the major active ingredient of the plant, is considered to be the most potent known hallucinogen of natural origin. This review surveys the current state of knowledge on the neurochemical, pharmacokinetic, and pharmacological properties of salvinorin A, the trends and motivation behind S. divinorum use, and the health problems among users of the plant's products. S. divinorum induces intense, but short-lived, psychedelic-like changes in mood and perception, with concomitant hallucinations and disorientation. Many websites have misinterpreted the limited existing research-based information on the side effects of salvia as evidence for its safety. However, data accumulated over the last few years indicate that potential health risks are associated with the use of S. divinorum, especially by teenagers, users of other substances of abuse, and individuals with underlying psychotic disturbances. Taken together, the data presented in this review point to the need for further basic and clinical studies to create a basis for the development of well-addressed prevention and treatment strategies. Copyright © 2013 John Wiley & Sons, Ltd.
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The multidisciplinary research on Salvia divinorum and its chemical principles is analyzed concerning whether the ethnobotany, phytochemistry, mental effects, and neuropharmacology of this sacred psychoactive plant and main principle clarify its experienced effects and divinatory uses. The scientific pursuit spans from the traditional practices, continues with the botanical identification, isolation of active molecules, characterization of mental and neural effects, possible therapeutic applications, and impinges upon the mind-body problem. The departure point is ethnopharmacology and therefore the traditional beliefs, ritual uses, and mental effects of this Mazatec sacred mint recorded during a 1973-1983 field research project are described. A water potion of crushed leaves produced short-lasting light-headedness, dysphoria, tactile and proprioceptive sensations, a sense of depersonalization, amplified sound perception, and an increase visual and auditory imagery, but not actual hallucinations. Similar effects were described using questionnaires and are attributable to salvinorin A, but cannot be explained solely by its specific and potent brain kappa-opioid receptor agonist activity. Some requirements for a feasible classification and mechanism of action of consciousness-altering products are proposed and include the activation of neural networks comprising several neurochemical systems. Top-down analyses should be undertaken in order to characterize such neural networks and eventually allowing to explore the differential ethnic effects. As is the case for other consciousness-altering preparations, a careful and encompassing research on this plant and principle can be consequential to endeavors ranging from the mind-body problem, a better understanding of shamanic ecstasy, to the potential generation of analgesic, antidepressant, and drug-abuse attenuating products.
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Stimulant use disorders are an unrelenting public health concern worldwide. Agonist replacement therapy is among the most effective strategies for managing substance use disorders including nicotine and opioid dependence. The present paper reviewed clinical data from human laboratory self-administration studies and clinical trials to determine whether agonist replacement therapy is a viable strategy for managing cocaine and/or amphetamine use disorders. The extant literature suggests that agonist replacement therapy may be effective for managing stimulant use disorders, however, the clinical selection of an agonist replacement medication likely needs to be based on the pharmacological mechanism of the medication and the stimulant abused by patients. Specifically, dopamine releasers appear most effective for reducing cocaine use whereas dopamine reuptake inhibitors appear most effective for reducing amphetamine use.
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Chronic use at high dose of illicit drugs, alcohol and tobacco is associated with physical disease. The relative physical harm of these substances has not been described before, but will benefit the guiding of policy measures about licit and illicit substances. The physical harm of 19 addictive substances (including alcohol and tobacco), consisting of toxicity and the risk and severity of somatic disease (not psychiatric disease) was assessed based on literature data and the professional opinion of experts using scores ranging from 0 (no physical harm) to 3 (very serious physical harm). For alcohol, tobacco and some illicit drugs strong associations between long-term use or use in high dose versus the risk of somatic disease have been described, whereas for other substances such data are not availible. Magic mushrooms, LSD and methylphenidate obtained relatively low scores (0.45-0.65) for physical harm, whereas relatively high scores were given for heroin (2.09), crack (2.32), alcohol (2.13) and tobacco (2.10). For cannabis, tobacco, and alcohol the estimated societal disease burden was higher than at individual level. The present ranking solely based on their physical harm was very similar to a previous ranking based on a combination of dependence liability, physical harm and social impairments.
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Sensitization refers to an increase in sensitivity to a drug and is believed to play a role in the etiology of substance use disorders. The purpose of the present study was to evaluate the ability of the mixed mu/kappa agonist nalbuphine to modulate sensitization to the locomotor and positive reinforcing effects of cocaine. Rats were habituated to a locomotor activity chamber and treated with saline (1.0 ml/kg, ip), cocaine (10 mg/kg, ip), or cocaine+nalbuphine (10 mg/kg, ip) every day for 10 days. Following locomotor activity testing, rats were implanted with intravenous catheters and cocaine self-administration was examined on fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement. Rats treated with cocaine exhibited a progressive increase in locomotor activity over the 10-day treatment period, and this effect was significantly reduced in rats treated with cocaine+nalbuphine. In self-administration tests, rats treated with cocaine exhibited significantly higher levels of responding at a threshold dose of cocaine (0.03 mg/kg/infusion) on both FR and PR schedules than rats treated with saline. This increase in responding at a threshold dose of cocaine was blocked completely in rats treated with cocaine+nalbuphine. These data suggest that nalbuphine attenuates the development of sensitization to the behavioral effects of cocaine.
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Salvia divinorum (Salvia) is an increasingly popular recreational drug amongst adolescents and young adults. Its primary active ingredient, Salvinorin A (SA)-a highly selective agonist at the κ opiate receptor-is believed to be one of the most potent naturally occurring hallucinogens. However, there is little experimental data on the effects of SA in humans. In a 3-day, double-blind, randomized, crossover, counterbalanced study, the behavioral, subjective, cognitive, psychophysiological, and endocrine effects of 0 mg, 8 mg, and 12 mg of inhaled SA were characterized in 10 healthy individuals who had previously used Salvia. SA produced psychotomimetic effects and perceptual alterations, including dissociative and somaesthetic effects, increased plasma cortisol and prolactin, and reduced resting electroencephalogram spectral power. The SA administration was associated with a rapid increase of its levels in the blood. SA did not produce euphoria, cognitive deficits, or changes in vital signs. The effects were transient and not dose-related. SA administration was very well-tolerated without acute or delayed adverse effects. SA produced a wide range of transient effects in healthy subjects. The perceptual altering effects and lack of euphoric effects would explain its intermittent use pattern. Such a profile would also suggest a low addictive potential similar to other hallucinogens and consistent with κ opiate receptor agonism. Further work is warranted to carefully characterize a full spectrum of its effects in humans, to elucidate the underlying mechanisms involved, and to explore the basis for individual variability in its effects.
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Kappa opioid agonists inhibit dopamine release from mesolimbic dopaminergic neurons and attenuate some behavioral effects of cocaine in rodents. Evidence that kappa opioid agonists may act as functional antagonists of cocaine led us to examine their interactions with cocaine's abuse-related effects in rhesus monkeys. In cocaine self-administration studies, four arylacetamides (U50,488, enadoline, (−) spiradoline and PD117302) and four benzomorphans (ethylketocyclazocine [EKC], bremazocine, Mr2033 and cyclazozine) each were administered as continuous infusions over 10 days. EKC, Mr2033, bremazocine, U50,488 and enadoline produced significant dose-dependent and sustained decreases in cocaine self-administration and also decreased food-maintained responding at some doses. Emesis and sedation were occasionally observed during the first two days of kappa agonist treatment, but tolerance developed rapidly to these effects. Cyclazocine, PD117302 and spiradoline did not significantly alter cocaine self-administration. The behavioral effects of EKC and U50,488 were antagonized by both the kappa opioid antagonist nor-binaltorphimine and the non-selective opioid antagonist naloxone. In general, compounds with mixed activity at both kappa and mu opioid receptors (e.g. EKC, Mr2033) decreased cocaine self-administration more consistently and with fewer or less severe undesirable side effects than more selective kappa agonists (e.g. U50,488, spiradoline). Although several kappa agonists decreased cocaine self-administration, EKC and U50,488 did not consistently block the discriminative stimulus effects of cocaine in monkeys trained to discriminate cocaine from saline. The extent to which kappa agonist-induced decreases in cocaine self-administration reflect an antagonism of cocaine's abuse-related effect remains to be determined.
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Addictions to cocaine or heroin/prescription opioids [short-acting μ-opioid receptor (MOPr) agonists] involve relapsing cycles, with experimentation/escalating use, withdrawal/abstinence, and relapse/re-escalation. κ-Opioid receptors (KOPr; encoded by OPRK1), and their endogenous agonists, the dynorphins (encoded by PDYN), have counter-modulatory effects on reward caused by cocaine or MOPr agonist exposure, and exhibit plasticity in addictive-like states. KOPr/dynorphin activation is implicated in depression/anxiety, often comorbid with addictions. In this opinion article we propose that particular stages of the addiction cycle are differentially affected by KOPr/dynorphin systems. Vulnerability and resilience can be due to pre-existing (e.g., genetic) factors, or epigenetic modifications of the OPRK1 or PDYN genes during the addiction cycle. Pharmacotherapeutic approaches limiting changes in KOPr/dynorphin tone, especially with KOPr partial agonists, may hold potential for the treatment of specific drug addictions and psychiatric comorbidity.
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Much effort has been devoted to research focused on pharmacotherapies for cocaine dependence yet there are no FDA-approved medications for this brain disease. Preclinical models have been essential to defining the central and peripheral effects produced by cocaine. Recent evidence suggests that cocaine exerts its reinforcing effects by acting on multiple neurotransmitter systems within mesocorticolimibic circuitry. Imaging studies in cocaine-dependent individuals have identified deficiencies in dopaminergic signaling primarily localized to corticolimbic areas. In addition to dysregulated striatal dopamine, norepinephrine and glutamate are also altered in cocaine dependence. In this review, we present these brain abnormalities as therapeutic targets for the treatment of cocaine dependence. We then survey promising medications that exert their therapeutic effects by presumably ameliorating these brain deficiencies. Correcting neurochemical deficits in cocaine-dependent individuals improves memory and impulse control, and reduces drug craving that may decrease cocaine use. We hypothesize that using medications aimed at reversing known neurochemical imbalances is likely to be more productive than current approaches. This view is also consistent with treatment paradigms used in neuropsychiatry and general medicine.
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Kappa opioid receptor (KOPr) activation antagonizes many cocaine-related behaviors but adverse side-effects such as sedation, dysphoria, and depression limit their therapeutic use. Recently, salvinorin A (Sal A), a naturally occurring KOPr agonist, has been shown to attenuate cocaine-induced drug seeking in a model of relapse in rats. The present study evaluated the effects of acute Sal A exposure on cocaine-induced hyperactivity and cocaine sensitization in rats. Acute treatment with a dose of Sal A that decreased drug seeking in a previous study (0.3 mg/kg) significantly attenuated the expression of cocaine sensitization. This dose of Sal A failed to affect spontaneous locomotion or to produce a conditioned taste aversion to a novel-tasting saccharin solution. However, Sal A decreased climbing and swimming time and increased time spent immobile in the forced swim test. These findings indicate that Sal A, just like traditional KOPr agonists, attenuates cocaine-induced behavioral sensitization but does not produce the adverse effect of conditioned aversion, suggesting improved potential compliance. However, prodepressive effects were also produced and these effects may limit the therapeutic potential.
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Repeated exposure to drugs of abuse and stress increase dynorphin, a κ opioid receptor (KOR) ligand, in the nucleus accumbens (NAc). Acute KOR activation produces dysphoria that might contribute to addictive behavior. How repeated KOR activation modulates reward circuitry is not understood. We used intracranial self-stimulation (ICSS), a method that provides a behavioral index of reward sensitivity, to measure the effects of repeated administration of the KOR agonist salvinorin A (salvA) (2 mg/kg) on the reward-potentiating effects of cocaine (5.0 mg/kg). In separate rats, we measured the effects of salvA on activation of extracellular signal regulated kinase (ERK), cyclic adenosine monophosphate (cAMP) response element binding protein, and c-Fos within the NAc. SalvA had biphasic effects on reward: an immediate effect was to decrease the rewarding impact of ICSS, whereas a delayed effect was to increase the rewarding impact of ICSS. Repeated salvA produced a net decrease in the reward-potentiating effects of cocaine. In the NAc, both acute and repeated salvA administration increased phosphorylated ERK, whereas only acute salvA increased c-Fos and repeated salvA increased phosphorylated cAMP response element binding protein. The KOR antagonist nor-binaltorphimine (20 mg/kg) blocked the immediate and delayed effects of salvA and prolonged the duration of cocaine effects in ICSS. Repeated salvA might trigger opponent processes such that "withdrawal" from the dysphoric effects of KOR activation is rewarding and decreases the net rewarding valence of cocaine. The temporal effects of salvA on ERK signaling suggest KOR-mediated engagement of distinct signaling pathways within the NAc that might contribute to biphasic effects on reward sensitivity.
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This study examined the effects of the kappa opioid agonists U50,488 and ethylketocyclazocine (EKC) on cocaine discrimination in rhesus monkeys trained to discriminate cocaine (0.4 mg/kg) from saline. Administration of U50,488 and EKC alone produced primarily saline-appropriate responding. Kappa agonist pretreatments produced variable effects on cocaine discrimination across monkeys, attenuating the discriminative stimulus effects of cocaine in some monkeys, but either having no effect on cocaine discrimination or enhancing the discriminative stimulus effects of cocaine in other monkeys. The effects of kappa agonists on cocaine discrimination were reversed by pretreatment with the opioid antagonist naloxone (1.0 mg/kg). These results indicate that kappa agonists do not consistently block the discriminative stimulus effects of cocaine in rhesus monkeys.
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Salvinorin A is a potent, selective nonnitrogenous kappa opioid agonist and the known psychoactive constituent of Salvia divinorum, a member of the mint family that has been used for centuries by Mazatec shamans of Mexico for divination and spiritual healing. S. divinorum has over the last several years gained increased popularity as a recreational drug. This is a double-blind, placebo controlled study of salvinorin A in 4 psychologically and physically healthy hallucinogen-using adults. Across sessions, participants inhaled 16 ascending doses of salvinorin A and 4 intermixed placebo doses under comfortable and supportive conditions. Doses ranged from 0.375 μg/kg to 21 μg/kg. Subject-rated drug strength was assessed every 2 min for 60 min after inhalation. Orderly time- and dose-related effects were observed. Drug strength ratings peaked at 2 min (first time point) and definite subjective effects were no longer present at approximately 20 min after inhalation. Dose-related increases were observed on questionnaire measures of mystical-type experience (Mysticism Scale) and subjective effects associated with classic serotonergic (5-HT2(A)) hallucinogens (Hallucinogen Rating Scale). Salvinorin A did not significantly increase heart rate or blood pressure. Participant narratives indicated intense experiences characterized by disruptions in vestibular and interoceptive signals (e.g., change in spatial orientation, pressure on the body) and unusual and sometimes recurring themes across sessions such as revisiting childhood memories, cartoon-like imagery, and contact with entities. Under these prepared and supportive conditions, salvinorin A occasioned a unique profile of subjective effects having similarities to classic hallucinogens, including mystical-type effects.
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Our previous work indicated that pretreatment with the selective kappa-opioid receptor (KOPr) agonist, U69593, attenuated the ability of priming injections of cocaine to reinstate extinguished cocaine-seeking behavior. The present study expanded these initial tests to include other traditional KOPr agonists, U50488H, spiradoline (SPR), and salvinorin A (Sal A), an active constituent of the plant Salvia divinorum. Following acquisition and stabilization of cocaine self-administration, cocaine-produced drug-seeking was measured. This test was conducted in a single day and comprised an initial phase of self-administration, followed by a phase of extinguished responding. The final phase examined reinstatement of extinguished cocaine self-administration followed by a priming injection of cocaine (20.0mg/kg, intraperitoneal (I.P.)) in combination with the various KOPr agonists. Cocaine-induced drug-seeking was attenuated by pretreatment with U69593 (0.3mg/kg, subcutaneous (S.C.)), U50488H (30.0mg/kg, I.P.), SPR (1.0, 3.0mg/kg, I.P.) and Sal A (0.3, 1.0mg/kg, I.P.). Sal A (0.3, 1.0mg/kg, I.P.) had no effect on operant responding to obtain sucrose reinforcement or on cocaine-induced hyperactivity. These findings show that Sal A, like other traditional KOPr agonists attenuates cocaine-induced drug-seeking behavior.
Article
Kappa opioid agonists attenuate some neurochemical and behavioral effects of cocaine and are being considered as potential treatments for cocaine dependence. The present study examined the effects of two kappa opioid agonists, the benzomorphan ethylketocyclazocine (EKC) and the arylacetamide U50,488, on cocaine self-administration in rhesus monkeys. Monkeys responded for 0.032 mg/kg/injection cocaine (i.v.) and 1 g banana-flavored food pellets during alternating daily sessions of cocaine and food availability. Chronic treatment for 10 consecutive days with EKC (0.0032-0.032 mg/kg/hr) or U50,488 (0.032-0.1 mg/kg/hr) dose-dependently decreased self-administration of cocaine unit doses at the peak of the cocaine dose-effect curve (0.01 and 0.032 mg/kg/injection). These decreases in cocaine self-administration were often sustained throughout the 10 days of treatment. Doses of EKC and U50,488 that decreased cocaine self-administration usually decreased food-maintained responding as well. In addition, EKC and U50,488 often produced emesis and sedation during the first few days of treatment, although tolerance appeared to develop rapidly to these effects. In general, EKC produced fewer undesirable effects than U50,488 at doses that decreased cocaine self-administration. The kappa antagonist norbinaltorphimine (3.2 mg/kg) did not affect responding maintained by cocaine or food. However, both norbinaltorphimine (3.2 mg/kg) and the opioid antagonist naloxone (1.0 mg/kg/hr) blocked the effects of EKC and U50,488. These results indicate that chronic administration of EKC and U50,588 produce a dose-dependent, kappa receptor-mediated and often sustained decrease in cocaine self-administration. However, these kappa agonists also produce undesirable behavioral effects that may complicate their use as treatments for cocaine dependence.
Article
There is accumulating evidence that kappa opioid agonists attenuate cocaine's behavioral effects, and we recently reported that the kappa opioid agonists ethylketocyclazocine (EKC) and U50-488 decreased cocaine self-administration by rhesus monkeys. In the present study, we first examined the effects of acute intramuscular administration of six kappa opioid agonists on responding maintained by food under an FR30 schedule. Each kappa agonist produced dose-dependent decreases in schedule controlled behavior, and the relative potencies were enadoline >/= bremazocine > Mr2033 >/= cyclazocine = spiradoline > PD117302. We then studied the effects of chronic administration of these kappa agonists in monkeys responding under a second order schedule of food delivery and cocaine self-administration. The effects of 10 days of intravenous treatment with three arylacetamides [enadoline (0.00032-0.0032 mg/kg/hr), (-) spiradoline (0.0032-0.018 mg/kg/hr), PD117302 (0.032-0.32 mg/kg/hr)] and three benzomorphans [bremazocine (0.00032-0.0032 mg/kg/hr), Mr2033 (0.0032-0.032 mg/kg/hr), cyclazocine (0.001-0.10 mg/kg/hr)] were compared with saline treatment. Enadoline (0.001 and 0.0032 mg/kg/hr), bremazocine (0.0032 mg/kg/hr) and Mr2033 (0.01 and 0.0032 mg/kg/hr) significantly decreased cocaine self-administration (0.01 mg/kg/injection) (P < .05-.01). Cyclazocine (0.001-0.10 mg/kg/hr), (-) spiradoline (0.0032-0.018 mg/kg/hr) and PD117302 (0.032-0.32 mg/kg/hr) had no significant effects on cocaine self-administration across the dose-range studied. When gradually increasing doses of enadoline (0.00032-0.01 mg/kg/hr) or Mr2033 (0.0032-0.032 mg/kg/hr) were administered over 28 consecutive days, cocaine self-administration was dose-dependently decreased in all monkeys. Food-maintained responding was usually decreased at doses that decreased cocaine self-administration. Adverse side effects (emesis and sedation) were transient, and laboratory indices of hematology and blood chemistry were normal throughout chronic enadoline and Mr2033 treatment. These data extend our earlier findings with EKC and U50,488 and suggest that kappa opioid agonists may be a useful approach to the development of new pharmacological treatments for cocaine dependence. The extent to which undesirable side effects may limit their clinical usefulness remains to be determined.
Article
Previous data have shown that the repeated administration of kappa-opioid receptor agonists attenuates the acute behavioral effects of cocaine. The site and mechanism by which kappa-agonists interact with this psychostimulant, however, are unknown. Accordingly, the present microdialysis study characterized the effects of prior, repeated administration of the selective kappa-opioid receptor agonist U69593 on basal and cocaine-evoked DA levels within the nucleus accumbens (NAC) and caudate putamen (CPU). The influence of U69593 treatment on the locomotor-activating effects of an acute cocaine challenge was also assessed. Rats received once daily injections of U69593 (0.16-0.32 mg/kg/day) or vehicle (1.0 ml/kg/day) for 3 days. The behavioral and neurochemical effects produced by an acute cocaine challenge (20 mg/kg i.p.) were assessed 2 days following treatment cessation. Administration of cocaine to control animals increased locomotor activity. This effect was attenuated in animals which had previously received U69593 (0.32 mg/kg/day x 3 days). Prior administration of U69593 failed to modify basal DA levels in either the NAC or CPU. Thus, 2 days following the cessation of U69593 treatment, dialysate DA levels did not differ from that of controls. Administration of cocaine to vehicle-treated animals increased dialysate levels of DA in both brain regions. However, in animals previously exposed to U69593 (0.32 mg/kg/day x 3 days), a significant enhancement in the response of DA neurons to cocaine was seen. These data demonstrate that prior, repeated administration of a selective kappa-opioid receptor agonist attenuates the locomotor-activating effects of cocaine and increases cocaine-evoked DA overflow in terminal projection areas of mesostriatal and mesolimbic DA neurons. These findings indicate that the behavioral interactions of kappa-agonists with cocaine observed in this and previous studies cannot be attributed to a presynaptic inhibition of DA release. Rather, they suggest that postsynaptic or non-DA mechanisms mediate the interaction of these agents with cocaine.
Article
Previous research has shown that kappa-opioid receptor agonists decrease intravenous cocaine self-administration. These agents also block the development of sensitization that occurs following repeated exposure to cocaine, which is thought to be important in the maintenance and reinstatement of compulsive drug-seeking behavior. This study was designed to determine the effects of the kappa-opioid receptor agonist, U69593, on the maintenance of cocaine self-administration and on the ability of a priming injection of cocaine to reinitiate drug-seeking. During daily test sessions, the dose-effect curve (0.015-1.0 mg/kg per infusion) was obtained by either repeatedly reducing the cocaine dose from a starting dose of 1.0 mg/kg per infusion or by repeatedly doubling the cocaine dose from a starting dose of 0.015 mg/kg per infusion. The effect of U69593 (0.0 or 0.32 mg/kg) on responding reinforced by different cocaine doses was determined. The effect of U69593 on the reinstatement of extinguished cocaine-taking behavior was measured in other groups. U69593 decreased responding maintained by low doses of cocaine, regardless of whether cocaine doses were presented in an ascending or descending order. Responding maintained by high doses was unaffected. In animals which received pretreatment with U69593, the priming effects of cocaine were significantly attenuated. The effects of U69593 were specific, since amphetamine-induced cocaine-seeking was not altered by prior administration of U69593. These findings demonstrate that U69593 attenuates cocaine self-administration and the reinstatement of drug-taking behavior which occurs in response to experimenter-administered cocaine. It is suggested that U69593 may decrease low dose cocaine self-administration by decreasing the priming effects of cocaine.
Article
It has been reported that the discriminative stimulus effects of cocaine in squirrel monkeys can be potentiated by mu opioid agonists and attenuated by kappa opioid agonists. The purpose of this study was to extend these observations by examining the effects of mu and kappa opioids agonists on the discriminative stimulus effects of d-amphetamine (AMPH). Five squirrel monkeys were trained to discriminate 0.3 mg/kg of AMPH (i.m.) from saline using a stimulus termination/avoidance task. AMPH and cocaine substituted dose dependently for the AMPH training stimulus in all five monkeys. The AMPH training dose was completely antagonized by 0.1 mg/kg of the D1 dopamine antagonist SCH 39166. When administered alone, the kappa agonist U69,593 substituted partially or completely for AMPH in four of five monkeys, the kappa agonist enadoline substituted completely for AMPH in two of five monkeys, and morphine substituted completely for AMPH in one monkey. In all five monkeys, pretreatment with some doses of U69,593 or enadoline attenuated the discriminative stimulus effects of AMPH; however, some doses of U69,593 and enadoline also potentiated the effects of AMPH in at least two monkeys. Morphine pretreatment potentiated the discriminative stimulus effects of AMPH in three monkeys and either attenuated or did not alter these effects in two monkeys. Morphine pretreatment did not significantly alter the discriminative stimulus effects of cocaine except in one monkey. These data indicate large individual differences in the abilities of mu and kappa opioid agonists to alter the discriminative stimulus effects of AMPH.
Article
Kappa-opioid receptor agonists prevent alterations in dopamine neurotransmission that occur in response to repeated cocaine administration. The present microdialysis study examined whether administration of the selective kappa-opioid receptor agonist U69593 with methamphetamine prevents alterations in dopamine levels produced by neurotoxic doses of methamphetamine. Swiss Webster mice were injected intraperitoneally with methamphetamine (10.0 mg/kg) or saline, four times in 1 day, at 2-h intervals. Prior to the first and third injection, they received U69593 (0.32 mg/kg s.c.) or vehicle. Microdialysis was conducted 3, 7, or 21 days later. Basal and K+-evoked (60 and 100 mM) dopamine overflow were reduced 3 days after methamphetamine administration. These effects were long-lasting in that they were still apparent 7 and 21 days after methamphetamine treatment. Intrastriatal (5.0 and 50 microM) or systemic (1.0-10.0 mg/kg) administration of methamphetamine increased dopamine concentrations in control animals. In mice preexposed to methamphetamine, methamphetamine-evoked dopamine overflow was reduced. In animals that had received methamphetamine with U69593, basal dopamine levels did not differ from those of vehicle-treated controls. U69593 treatment attenuated the decrease in K+-evoked dopamine produced by prior methamphetamine exposure. The reduction in methamphetamine-evoked dopamine levels was also attenuated. The administration of U69593 alone did not modify basal or stimulus-evoked dopamine levels. These data demonstrate that repeated methamphetamine administration reduces presynaptic dopamine neuronal function in mouse striatum and that co-administration of a selective kappa-opioid receptor agonist with methamphetamine attenuates these effects. U69593 treatment did not modify the hyperthermic effects of methamphetamine, indicating that this kappa-opioid receptor agonist selectively attenuates methamphetamine-induced alterations in dopamine neurotransmission.
Article
Mesolimbic dopaminergic neurotransmission plays a critical role in the locomotor effects of psychostimulant drugs, but a general involvement in the induction of long-term psychostimulant sensitization is questionable. By influencing dopaminergic neurotransmission, opioid drugs can alter the behavioral effects of psychostimulants. The effects of the kappa-opioid receptor agonists bremazocine, U69593, and U50488H on the locomotor stimulant and the long-term sensitizing effects of amphetamine and cocaine were investigated in rats. Unlike U69593 and U50488H, bremazocine is also an antagonist at mu- and delta-opioid receptors, as well as an agonist at a subtype of delta-opioid receptors inhibiting dopamine D1 receptor-stimulated adenylate cyclase. Bremazocine, U69593, and U50488H were administered prior to amphetamine and cocaine, and locomotor activity was measured. In separate studies, the opioids were co-administered with amphetamine and cocaine for 5 days, and locomotor sensitization was assessed 3 weeks post-treatment. Bremazocine and U69593 attenuated the psychomotor stimulant effects of amphetamine and cocaine. U50488H attenuated the locomotor effect of cocaine and biphasically affected amphetamine-induced locomotion, i.e., suppression followed by stimulation. Bremazocine prevented the development of amphetamine-induced but not cocaine-induced long-term sensitization. Neither U69593 nor U50448H affected the induction of long-term amphetamine or cocaine sensitization. In agreement with previous studies, the present data suggest that differential mechanisms underlie the acute stimulant versus the long-term sensitizing effects of psychostimulants, and the induction of long-term sensitization by amphetamine versus cocaine. Stimulation of kappa-opioid receptors does not seem to block the induction of long-term psychostimulant sensitization. Thus, bremazocine is likely to block the induction of amphetamine sensitization through a non-kappa-opioid receptor mechanism. We suggest that this effect of bremazocine is the result of its unique agonist action at a subtype of delta-opioid receptors, thereby acting as a functional dopamine D1 receptor antagonist. This would be consistent with the literature showing that the induction of long-term amphetamine sensitization depends on the activation of dopamine D1 receptors. In addition, the present data are in keeping with studies showing that dopamine neurotransmission is not critical for the induction of long-term cocaine sensitization.
Article
Results of a previous study indicated that prior administration of the kappa-opioid receptor agonist, U69593, blocked the ability of cocaine to reinstate extinguished cocaine-taking behavior. In order to determine whether the effect of U69593 was specific to cocaine or was common to cocaine seeking produced by other dopamine uptake inhibitors, the effects of U69593 on cocaine seeking produced by experimenter-administered injections of cocaine, the dopamine uptake inhibitor, GBR 12909, or the cocaine analogs, WIN 35,428 and RTI-55, were compared. Reinstatement of extinguished cocaine-taking behavior was measured for rats that received injections of the kappa-opioid agonist, U69593 (0.0 or 0.32 mg/kg, SC), 15 min prior to injections of cocaine- (0.0-20.0 mg/kg, IP), GBR 12909- (0.0-30.0 mg/kg, IP), WIN 35.428- (0.0-3.0 mg/kg, IP) or RTI-55 (0.0-0.50 mg/kg, IP). All of the drugs produced a dose-dependent reinstatement of extinguished cocaine-taking behavior. However, only the effects of cocaine and RTI-55 were attenuated by prior administration of U69593 (0.32 mg/kg, SC). The U69593-produced attenuation of cocaine-produced cocaine seeking was reversed by prior administration of the kappa-opioid antagonist, norbinaltorphimine (30.0 microg, ICV), indicating that the effect was mediated by central kappa-opioid receptors. The failure of U69593 to attenuate GBR 12909- or WIN 35,428-produced cocaine seeking suggests that the effect of this kappa-opioid receptor agonist on cocaine seeking is not mediated by interactions at the dopamine transporter. The ability of U69593 to attenuate RTI-55-produced cocaine seeking raises the possibility that kappa-opioids and cocaine may interact at common sites on the serotonin transporter.
Article
The repeated administration of selective kappa-opioid receptor agonists prevents the locomotor activation produced by acute cocaine administration and the development of cocaine-induced behavioral sensitization. Previous studies have shown that dopamine (DA) D2 autoreceptors modulate the synthesis and release of DA in the striatum. Evidence that kappa agonist treatment downregulates DA D2 receptors in this same brain region has recently been obtained. Accordingly, the present studies were undertaken to examine the influence of repeated kappa-opioid receptor agonist administration on pre- and postsynaptic DA D2 receptor function in the dorsal striatum using pre- and postsynaptic receptor-selective doses of quinpirole. Rats were injected once daily with the selective kappa-opioid receptor agonist U69593 (0.16-0.32 mg/kg s.c.) or vehicle for 3 days. Microdialysis studies assessing basal and quinpirole-evoked (0.05 mg/kg s.c.) DA levels were conducted 2 days later. Basal and quinpirole-stimulated locomotor activity were assessed in a parallel group of animals. The no-net flux method of quantitative microdialysis revealed no effect of U69593 on basal DA dynamics, in that extracellular DA concentration and extraction fraction did not differ in control and U69593-treated animals. Acute administration of quinpirole significantly decreased striatal DA levels in control animals, but in animals treated with U69593, the inhibitory effects of quinpirole were significantly reduced. Quinpirole produced a dose-related increase in locomotor activity in control animals, and this effect was significantly attenuated in U69593-treated animals. These data reveal that prior repeated administration of a selective kappa-opioid receptor agonist attenuates quinpirole-induced alterations in DA neurotransmission and locomotor activity. These results suggest that both pre- and postsynaptic striatal DA D2 receptors may be downregulated following repeated kappa-opioid receptor agonist administration. Synapse 39:343-350, 2001. Published 2001 Wiley-Liss, Inc.
Article
Previous studies showed that prior administration of kappa-opioid agonists decreased the development of sensitization to some of the behavioral effects of cocaine. The present study sought to determine whether the development of sensitization to cocaine's reinforcing effects was also sensitive to antagonism by kappa-opioid agonists. During a pretreatment phase, the kappa-opioid agonist, U69593 (0.0 or 0.32 mg/kg) was administered prior to (1) 2 daily injections of cocaine (0.0 or 20.0 mg/kg), or (2) cocaine or saline administered via a yoking procedure. Cocaine pretreatment decreased the latency to acquisition of cocaine self-administration. However, prior administration of U69593 during the pretreatment phase failed to attenuate the development of this sensitized response to cocaine's reinforcing effect. In other groups, the effect of acute U69593 pretreatment on the maintenance of cocaine self-administration was examined during a 10 hr session. During training and testing, a stimulus was associated with each self-administered cocaine infusion for one group whereas responding of another group was reinforced by a cocaine infusion alone. On the test day, pretreatment with U69593 (0.32 mg/kg) decreased responding during each hour of the 10 hr session for the group that was reinforced with cocaine plus the cocaine-associated stimulus. U69593 failed to produce a long-lasting disruption of cocaine self-administration for rats that were trained and tested without the cocaine-associated stimulus. These data suggest that the acquisition and maintenance of cocaine self-administration are differentially sensitive to manipulations of kappa-opioid systems. Further, the disruption of cocaine self-administration by U69593 may be due to interactions with mechanisms that underlie facilitative effects of stimuli that have been associated with self-administered cocaine infusions.
Article
The repeated, intermittent use of cocaine and other drugs of abuse produces profound and often long-lasting alterations in behavior and brain chemistry. It has been suggested that these consequences of drug use play a critical role in drug craving and relapse to addiction. This article reviews the effects of psychostimulant administration on dopaminergic and excitatory amino acid neurotransmission in brain regions comprising the brain's motive circuit and provides evidence that the activation of endogenous kappa-opioid receptor systems in these regions opposes the behavioral and neurochemical consequences of repeated drug use. The role of this opioid system in mediating alterations in mood and affect that occur during abstinence from repeated psychostimulant use are also discussed.
Article
Previous research has indicated that pretreatment with the kappa-opioid receptor agonist, U69593, decreased the ability of experimenter-administered cocaine to reinstate extinguished cocaine self-administration behavior. This effect was specific to cocaine-produced drug seeking since U69593 failed to attenuate the ability of experimenter-administered amphetamine to reinstate extinguished cocaine self-administration behavior. One possibility is that U69593 selectively attenuates the behavioral effects of the drug that was originally self-administered. In order to test this hypothesis, the present study examined the effect of U69593 (0.0 or 0.32 mg/kg) on the reinstatement of extinguished amphetamine self-administration behavior produced by experimenter-administered injections of cocaine and amphetamine. Following extinction of amphetamine self-administration (0.04 mg/kg/infusion) the ability of cocaine (0.0, 5.0, 10.0 or 20.0 mg/kg) or amphetamine (0.0, 0.3, 1.0 or 3.0 mg/kg) to reinstate extinguished self-administration behavior was measured. Both drugs reinstated extinguished responding and the reinstatement was attenuated by pretreatment with U69593. The data indicate that the ability of U69593 to decrease drug seeking is not restricted to subjects experienced with cocaine self-administration. Self-administration history does, however, determine the effect of U69593 on amphetamine-produced drug seeking.
Article
Preclinical studies have demonstrated that κ-opioid agonists can attenuate the neurochemical and behavioral effects of cocaine that are related to its reinforcing efficacy, suggesting that κ-agonists may serve as pharmacotherapies for cocaine dependence. This 8-week inpatient study examined the ability of enadoline, a selective and high-efficacy κ-agonist, and butorphanol, a mixed agonist with intermediate efficacy at both μ-and κ-receptors, to reduce the direct pharmacodynamic effects and self-administration of intravenous cocaine in humans (n = 8). Acute doses of intramuscular enadoline (20, 40, and 80 μg/kg), butorphanol (1.5, 3, and 6 mg/70 kg) and placebo were examined separately as pretreatments during each of three test sessions with cocaine in a constrained random order. A cocaine dose-effect session (0, 20, and 40 mg cocaine i.v., 1 h apart) examined direct pharmacodynamic interactions on subjective and physiological indices; self-administration sessions examined choice behavior for cocaine (40 mg i.v. for six trials) versus money 1) in the presence of a sample cocaine dose with money choices presented in ascending value, and 2) in the absence of a sample dose with money choices presented in descending values. Enadoline (80 μg/70 kg) significantly (p < 0.05) reduced some of the positive subjective effects of cocaine (e.g., ratings of "high"), while butorphanol failed to modify subjective responses. Both agents were safely tolerated in combination with cocaine without adverse physiological responses. Cocaine self-administration was significantly greater across all pretreatment conditions when the sample dose was given and ascending money choices were used. Enadoline and butorphanol failed to modify cocaine self-administration. These data suggest that these κ-agonists may be safely administered in the presence of cocaine but do not produce significant attenuation of cocaine's direct effects or self-administration under these acute dosing conditions.
Article
The availability of the highly selective and specific kappa opioid agonist enadoline provides an opportunity to explore the function of kappa receptors in humans and their potential utility as a target for substance abuse pharmacotherapy development. The purpose of this study was to characterize the pharmacodynamic effects of enadoline, a selective kappa agonist, and to compare it with butorphanol, a mixed mu/kappa agonist, and hydromorphone, a mu agonist, in humans. Pilot evaluation (n=3) served to establish intramuscular doses of enadoline (20, 40, 80, and 160 microg/70 kg), butorphanol (1.5, 3, 6, and 12 mg/70 kg), and hydromorphone (1.5, 3, and 6 mg/70 kg) of comparable activity. These acute doses were examined under double-blind, placebo-controlled and constrained randomized conditions with a minimum of 72 h between tests in volunteers with polysubstance abuse histories (n=6). Physiological and subject- and observer-rated measures were collected 30 min before and for 4 h after administration. Enadoline significantly increased measures of sedation, confusion and dizziness, produced visual distortions and feelings of depersonalization, and increased urinary output. The highest dose (160 microg/70 kg) was not tolerated and led to psychotomimetic effects. Hydromorphone produced prototypic mu opioid effects including respiratory depression, miosis, and euphoria. Butorphanol was most similar to hydromorphone and shared few effects with enadoline. These results are discussed with respect to the potential use and safety of kappa agonists for clinical indications.
Article
There is increasing evidence that kappa-opioid receptor agonists modulate cocaine-maintained behavior, and limited findings implicate the involvement of kappa-opioid receptors in ethanol-maintained behaviors. The purpose of the present study was to investigate the effects of bremazocine, a kappa-opioid agonist, on the self-administration of smoked cocaine base and oral ethanol in rhesus monkeys (Macaca mulatta). To determine the selectivity of bremazocine, the effects of bremazocine pretreatment on the oral self-administration of phencyclidine (PCP), saccharin, and food were also examined. Adult male rhesus monkeys were trained to self-administer oral ethanol, PCP, saccharin (n = 8), food (n = 6), or smoked cocaine base (n = 6) and water during daily sessions. Bremazocine (0.00032-, 0.001-, and 0.0025-mg/kg i.m.) injections were given 15 min before session. The 4 days of stable behavior before pretreatment served as baseline. Demand curves (consumption x fixed ratio; FR) were obtained for smoked cocaine base, ethanol, and PCP by varying the cost (FR) of drug deliveries and measuring consumption (deliveries). Bremazocine (0.001 mg/kg) was administered at each FR value in nonsystematic order. Results indicate that bremazocine dose dependently reduced cocaine, ethanol, PCP, and saccharin intake. Food intake was affected less by bremazocine than the other substances in five of the six monkeys. Generally, bremazocine treatment reduced the demand for cocaine, ethanol, and PCP as well as other measures of response strength. These results extend the findings that kappa-agonists reduce the self-administration of drug and nondrug reinforcers to smoked cocaine base and oral ethanol, PCP, and saccharin in rhesus monkeys.