Enhanced sensitivity of pituitary β-endorphin to ethanol in subjects at high risk of alcoholism
Department of Psychiatry, McGill University, and Douglas Hospital Research Centre, Verdun, Quebec. Archives of General Psychiatry
(Impact Factor: 14.48).
Previous studies have demonstrated that a moderate dose of ethanol induced a significant increase in the plasma beta-endorphin content of subjects from families with a history of alcoholism (high risk (HR)), but not subjects from families without a history of alcoholism (low risk (LR)). The objective of this study was to examine the response of the pituitary beta-endorphin and adrenal cortisol systems to various concentrations of ethanol in male and female subjects at high and low risk of the future development of alcoholism.
All subjects participated in four experimental sessions. In each session the subjects were given a drink containing one of the following doses of ethanol: 0, 0.25, 0.50, and 0.75 g of ethanol per kilogram of body weight (for a 60- to 70-kg individual). Blood samples were taken at 0 minutes and at 15, 45, 120, and 180 minutes after the drink for estimation of the blood alcohol, plasma beta-endorphin, and plasma cortisol levels.
The concentration of alcohol in the blood at various intervals after the drink was similar among the subjects, regardless of the risk group. Ethanol increased the plasma level of beta-endorphin-related peptides of the HR but not of the LR subjects in a dose-dependent manner. All subjects showed a small decrease in plasma cortisol level with time, but ethanol ingestion did not significantly alter the plasma cortisol levels.
This study indicates that the pituitary beta-endorphin system, but not the adrenal cortisol system, of the HR subjects shows an enhanced sensitivity to ethanol, which may be an important factor in controlling ethanol consumption.
Available from: jpet.aspetjournals.org
- "In 1994, naltrexone (compound 1; Scheme 1), a pure opioid m-receptor antagonist with relatively low affinity for d-and k-opioid receptors and no abuse potential (Tabakoff and Hoffman, 1983), was approved by the US Food and Drug Administration for treatment of alcoholism. A number of studies suggest that alcohol interacts with endogenous opioid systems (Grisel et al., 1995; Gianoulakis et al., 1996). Antagonizing opioid receptors decreases the effects of alcohol-mediated pleasure-inducing endogenous opioids. "
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ABSTRACT: A substituted aryl amide derivative of 6-naltrexamine, compound 5, previously shown to be a potent kappa opioid receptor antagonist, was used to characterize the physicochemical properties and efficacy to decrease alcohol self-administration in alcohol-preferring rats (P-rats) and binge-like P-rats. Previous studies showed that compounds closely related to 5 possessed good blood-brain barrier penetrating properties. Pharmacokinetic studies showed that 5 had acceptable bioavailability. In contrast to other kappa receptor antagonists (i.e., nor-BNI) compound 5 showed favorable drug-like properties and further studies were done. Safety studies showed that 5 was not hepatotoxic at doses 200-fold greater than an efficacious dose. The effect of 5 or naltrexone on the hepatotoxicity of thiobenzamide was investigated. In contrast to naltrexone that exacerbated thiobenzamide-mediated hepatotoxicity, 5 was observed to be hepatoprotective. Based on the physicochemical properties of 5, the compound was examined in rat animal models of alcohol self-administration. The inhibition of ethanol self-administration by 5 in alcohol-dependent or alcohol-nondependent P-rats trained to self-administer a 10 % (w/v) ethanol solution, utilizing operant techniques showed very potent efficacy (i.e., estimated ED50 value 4-5 μg/kg). In a binge-like P-rat animal model, inhibition of alcohol self-administration by 5 had an estimated ED50 value of 8 μg/kg. The results suggest that 5 is a potent drug-like kappa opioid receptor antagonist of utility in alcohol cessation medications development.
Journal of Pharmacology and Experimental Therapeutics 05/2014; 350(1). DOI:10.1124/jpet.114.214262 · 3.97 Impact Factor
Available from: Brendan M Walker
- "In accordance with the OPT, if alcohol-mediated MOR or DOR stimulation (Marinelli et al., 2004, 2005; Lam et al., 2008; Jarjour et al., 2009) produces positive hedonic states (Amalric et al., 1987; Shippenberg et al., 1987), then a compensatory mechanism could be increased DYN and/or function of KORs, stimulation of which produces negative hedonic states (Mucha and Herz, 1985). Under conditions of chronic alcohol use (see Figure 2), the predicted response of the endogenous opioidergic system would be attenuated MOR signaling and exacerbated DYN/KOR system activity, both of which are supported in the literature (Gianoulakis et al., 1996; Przewlocka et al., 1997; Turchan et al., 1999; Chen and Lawrence, 2000; Lindholm et al., 2000; Saland et al., 2004; Lindholm et al., 2007). In addition, chronic alcohol exposure has been shown to alter various neuropeptide systems (e.g., corticotropin-releasing factor (CRF), neuropeptide Y and nociceptin; Cowen and Lawrence, 2006; Ciccocioppo et al., 2009; Koob, 2010) that may contribute to the development of alcohol dependence and/or negative affective states. "
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ABSTRACT: Alcoholism is a chronic relapsing disorder characterized by continued alcohol use despite numerous adverse consequences. Alcohol has been shown to interact with numerous neurotransmitter systems to exert its pharmacological effects. The endogenous opioid system (EOS) has been strongly implicated in the positive and negative reinforcing effects of alcohol. Traditionally recognized as dysphoric/anhedonic in nature, the dynorphin/kappa-opioid receptor (DYN/KOR) system has recently received considerable attention due to evidence suggesting that an upregulated DYN/KOR system may be a critical contributor to the complex factors that result in escalated alcohol consumption once dependent. The present review will discuss alcohol-induced plasticity in the DYN/KOR system and how these neuroadaptations could contribute to excessive alcohol seeking and consumption.
Frontiers in Molecular Neuroscience 09/2012; 5:95. DOI:10.3389/fnmol.2012.00095 · 4.08 Impact Factor
Available from: Spencer Bujarski
- "A few studies however, have not found support for the efficacy of naltrexone (Killeen et al., 2004; Kranzler et al., 2000; Krystal et al., 2001). Alcohol has a complex pharmacological profile involving affinity for multiple receptor types; the reinforcing effects are thought to be due to the combined release of endogenous opioids like β-endorphin and dopamine (from the midbrain), targeting neurons in the nucleus accumbens (NAc) downstream (Gianoulakis et al., 1996; Volpicelli, 2001). Current models of the effects of naltrexone posit that it acts by diminishing the dopamine response to ethanol in the NAc, which has been supported by pre-clinical research (Benjamin et al., 1993). "
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ABSTRACT: Naltrexone, one of four FDA-approved pharmacotherapies for alcohol dependence, has shown moderate efficacy in clinical trials. Pharmacogenetic effects have been reported such that allelic variation at the gene encoding the mu-opioid receptor (OPRM1, rs1799971) predicts naltrexone-induced blunting of the positively reinforcing effects of alcohol. However, naltrexone also binds, albeit to a lesser degree, to kappa and delta opioid receptors in the brain. This alternate binding presents the possibility that single nucleotide polymorphisms (SNPs) in the kappa and delta opioid receptor (OPRK1 and OPRD1) genes may contribute to naltrexone pharmacogenetics. Therefore, the goal of this exploratory study was to re-examine data from a double-blind placebo controlled laboratory trial of naltrexone for pharmacogenetic effects at kappa and delta opioid receptor tag SNPs. Participants were 40 heavy drinkers (12 female) who underwent an intravenous alcohol challenge paradigm after receiving naltrexone (50mg) or placebo in randomized and crossover fashion. Dependent variables were self-reported alcohol-induced stimulation, sedation, and craving. Multilevel models revealed a significant Naltrexone×OPRK1 Genotype (rs997917) interaction predicting alcohol-induced sedation, such that TT homozygotes reported lower naltrexone-induced alcohol sedation as compared to carriers of the C allele. Moreover, there was a significant Naltrexone×OPRD1 Genotype (rs4654327) interaction predicting alcohol-induced stimulation and craving, such that carriers of the A allele at this locus reported greater naltrexone-induced blunting of alcohol stimulation and alcohol craving compared to GG homozygotes. These findings suggest that additional pharmacogenetic effects in the opioid receptor system may account for individual differences in response to naltrexone in the human laboratory.
Pharmacology Biochemistry and Behavior 08/2012; 103(2):253-259. DOI:10.1016/j.pbb.2012.08.019 · 2.78 Impact Factor
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