Varenicline effects on cocaine self administration and reinstatement behavior
This study tested the effects of the nicotine addiction treatment varenicline on cocaine self administration (SA) and reinstatement. In one SA experiment, rats were trained to self-administer cocaine (0.75 mg/kg/infusion). Thereafter, daily SA sessions continued as before except that every fourth session was preceded by a presession injection of varenicline (0.0, 0.3, 1.0 and 2.0 mg/kg, SC, 50-min presession). In three reinstatement experiments, animals were exposed sequentially to SA training, extinction training, and several reinstatement test sessions. In two of the reinstatement experiments, cocaine-seeking was reinstated by presentation of cocaine-predictive cues at the onset of the test session (cue reinstatement). In a third reinstatement experiment, cocaine-seeking was reinstated by a presession injection of cocaine (drug reinstatement). Each reinstatement session was preceded by an injection of either vehicle or varenicline (dose range of 0.1-2.0 mg/kg). The SA and reinstatement experiments showed that low-dose varenicline decreases reinstatement behavior, without significantly affecting cocaine SA. In contrast, high-dose varenicline increases reinstatement of cocaine-directed behavior and decreases cocaine SA. A control study showed that sucrose-directed behavior is unaltered by varenicline. On the basis of these findings, low-varenicline doses might decrease relapse in cocaine-addicted individuals, but high doses of varenicline might have the opposite effect.
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[Show abstract] [Hide abstract] ABSTRACT: Alcohol and drug dependence are serious public health problems worldwide. The prevalence of alcohol and drug dependence in the United States and other parts of the world is significant. Given the limitations in the efficacy of current pharmacotherapies to treat these disorders, research in developing alternative pharmacotherapies continues. Preclinical and clinical evidence thus far has indicated that brain nicotinic acetylcholine receptors (nAChRs) are important pharmacological targets for the development of medications to treat alcohol and drug dependence. The nAChRs are a super family of ligand gated ion channels, and are expressed throughout the brain with twelve neuronal nAChR subunits (α2–α10 and β2–β4) identified. Here, we review preclinical and clinical evidence involving a number of nAChR ligands that target different nAChR subtypes in alcohol and nicotine addiction. The important ligands include cytisine, lobeline, mecamylamine, varenicline, sazetidine A and others that target α4β2∗ nAChR subtypes as small molecule modulators of the brain nicotinic cholinergic system are also discussed. Taken together, both preclinical and clinical data exist that support nAChR–based ligands as promising therapeutic agents for the treatment of alcohol and drug dependence.0Comments 9Citations
- "With regard to other psychostimulants, a number of nACR antagonists were found to decrease cocaine self-administration, prevent cue-induced craving for cocaine, and to decrease cocaine effects in a place preference paradigm or reduce cocaine-induced behavioral sensitization (Levin et al., 2000; Zachariou et al., 2001; Champtiaux et al., 2006; Hansen and Mark, 2007) suggesting a direct involvement of nAChRs in cocaine-taking and -seeking behavior. In addition, recent studies indicate that varenicline reduces cocaine-induced reward in rodents and humans (Guillem and Peoples, 2010; Plebani et al., 2012). In contrast, varenicline was found ineffective in reducing cocaine self-administration in a primate model (Gould et al., 2011), indicating mixed effects across models which may be due to species' differences . "
[Show abstract] [Hide abstract] ABSTRACT: Exposure to environmental stimuli conditioned to nicotine consumption critically contributes to the high relapse rates of tobacco smoking. Our previous work demonstrated that non-selective blockade of nicotinic acetylcholine receptors (nAChRs) reversed the cue-induced reinstatement of nicotine seeking, indicating a role for cholinergic neurotransmission in the mediation of the conditioned incentive properties of nicotine cues. The present study further examined the relative roles of the two major nAChR subtypes, α4β2 and α7, in the cue-induced reinstatement of nicotine seeking. Male Sprague-Dawley rats were trained to intravenously self-administer nicotine (0.03 mg/kg/infusion, free base) on a fixed-ratio 5 schedule of reinforcement. A nicotine-conditioned cue was established by associating a sensory stimulus with each nicotine infusion. After nicotine-maintained responding was extinguished by withholding the nicotine infusion and its paired cue, reinstatement test sessions were conducted with re-presentation of the cue but without the availability of nicotine. Thirty minutes before the tests, the rats were administered the α4β2-selective antagonist dihydro-β-erythroidine (DHβE) and α7-selective antagonist methyllycaconitine (MLA). Pretreatment with MLA, but not DHβE, significantly reduced the magnitude of the cue-induced reinstatement of responses on the active, previously nicotine-reinforced lever. In different sets of rats, MLA altered neither nicotine self-administration nor cue-induced reinstatement of food seeking. These results demonstrate that activation of α7 nAChRs participates in the mediation of the conditioned incentive properties of nicotine cues and suggest that α7 nAChRs may be a promising target for the development of medications for the prevention of cue-induced smoking relapse.0Comments 7Citations
- "Interestingly, Wouda et al. (2011) found that varenicline effectively attenuated the cue-induced reinstatement of alcohol-seeking behaviour. Together with another report (Guillem and Peoples, 2010), in which varenicline at lower doses reduced the cue-induced reinstatement of cocaine-seeking, these results suggests a role for α4β2 nAChRs in the motivational effects of cues conditioned to alcohol and cocaine but not nicotine. Elucidating such a significant difference between nicotine and other drugs of abuse and the involvement of associative learning and memory processes warrants future studies. "
[Show abstract] [Hide abstract] ABSTRACT: To thrive in any given environment, mobile creatures must be able to learn from the outcomes of both successful and disappointing events. To learn from success, the brain relies on signals originating in the ventral tegmental area and substantia nigra that result in increased release of dopamine in the striatum. Recently, it was shown that to learn from disappointment the brain relies on signals originating in the lateral habenula, which indirectly inhibit dopaminergic activity. The habenula is a small brain region that has been shown in mice to be critical for the appearance of nicotine withdrawal symptoms. The nicotinic acetylcholine receptor subunits expressed in the medial habenula are necessary to observe withdrawal symptoms in mice, and blocking nicotinic activity in the medial habenula only is sufficient to precipitate withdrawal in dependent mice. In addition, recent genome wide association studies have shown that in humans, genetic variants in the same nicotinic receptor subunits are at least partially responsible for the genetic predisposition to become a smoker. The habenula is linked not only to nicotine, but also to the effects of several other drugs. We postulate that the continuous use of drugs of abuse results in habenular hyperactivity as a compensatory mechanism for artificially elevated dopamine release. Drug withdrawal would then result in non-compensated habenular hyperactivity, and could be thought of as a state of continuous disappointment (or a negative emotional state), driving repeated drug use. We believe that drugs that alter habenular activity may be effective therapies against tobacco smoke and drug addiction in general.0Comments 25Citations
- "Varenicline's effects on cocaine self-administration and reinstatement were studied on rats. Low doses of varenicline diminished cocaine reinstatement, while high doses increased it, but decreased self-administration . Varenicline has also been shown to work against alcohol dependence in mice: in doses similar to those used to reduce nicotine reward, varenicline reduced ethanol but not sucrose seeking on a self-administration drinking paradigm. "
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