Biperiden (an M1 antagonist) reduces memory consolidation of cocaine-conditioned place preference

Preliminary investigation of the administration of biperiden to reduce relapses in individuals with cocaine/crack user disorder: A randomized controlled clinical trial

BACKGROUND

Several studies have demonstrated that ACh modulates the dopaminergic circuit in the nucleus accumbens, and its blockade appears to be associated with the inhibition of the reinforced effect or the increase in dopamine caused by cocaine use. The objective of this study was to evaluate the effect of biperiden (a muscarinic receptor antagonist with a relatively higher affinity for the M1 receptor) on crack/cocaine use relapse compared to a control group that received placebo.

METHODS

This study is a double-blind, randomized, placebo-controlled clinical trial. The intervention group received 2 mg of biperiden, 3 times a day, for a period of 3 months. The control group received identical placebo capsules, at the same frequency and over the same period. All participants were followed for a period of six months.

RESULTS

The sample comprised 128 people, with 61 in the control group and 67 in the biperiden group. Lower substance consumption was observed in the group that received biperiden treatment two (bT2 = -2.2 [-3.3; -1.0], p < 0.001) and six months (bT4 = -6, 2 [-8.6; -3.9], p < 0.001) after the beginning of the intervention. The biperiden group had a higher latency until a possible first day of consumption, in the same evaluation periods (bT2 = 0.26 [0.080; 0.44], p = 0.004; bT4 = 0.63 [0.32; 0.93], p < 0.001).

CONCLUSIONS

Despite the major limitations of the present study, the group that received biperiden reduced the number of days of cocaine/crack use and showed an increase in the latency time for relapse. More studies are needed to confirm the utility of this approach.

Biperiden reverses the increase in 50-kHz ultrasonic vocalizations but not the increase in locomotor activity induced by cocaine

Cocaine use disorder (CUD) is a worldwide public health problem, associated with severe psychosocial and economic impacts. Currently, no FDA-approved treatment is available for CUD. However, an emerging body of evidence from clinical and preclinical studies suggests that biperiden, an M1 muscarinic receptor antagonist, presents potential therapeutic use for CUD. These studies have suggested that biperiden may reduce the reinforcing effects of cocaine. It is well established that rodents emit 50-kHz ultrasonic vocalizations (USV) in response to natural rewards and stimulant drugs, including cocaine. Nonetheless, the effects of biperiden on the cocaine-induced increase of 50-kHz USV remains unknown. Here, we hypothesized that biperiden could antagonize the acute effects of cocaine administration on rat 50-kHz USV. To test this hypothesis, adult male Wistar rats were divided into four experimental groups: saline, 5 mg/kg biperiden, 10 mg/kg cocaine, and biperiden/cocaine (5 and 10 mg/kg, i.p., respectively). USV and locomotor activity were recorded in baseline and test sessions. As expected, cocaine administration significantly increased the number of 50-kHz USV. Biperiden administration effectively antagonized the increase in 50-kHz USV induced by cocaine. Cocaine administration also increased the emission of trill and mixed 50 kHz USV subtypes and this effect was antagonized by biperiden. Additionally, we showed that biperiden did not affect the cocaine-induced increase in locomotor activity, although biperiden administration per se increased locomotor activity. In conclusion, our findings indicate that administering biperiden acutely reduces the positive affective effects of cocaine, as demonstrated by its ability to inhibit the increase in 50-kHz USV.

Effects of biperiden (cholinergic muscarinic m1/m4 receptor antagonist) on ethanol conditioned place preference in mice

BACKGROUND

Previous studies suggest that muscarinic cholinergic receptors might act upon the dopamine release in the mesolimbic system and alter drug-reinforcing values related to drug craving.

AIMS

We examined the effects of systemic biperiden administration, a muscarinic cholinergic (M1/M4) receptor antagonist, on ethanol (dose of 2 g/Kg) conditioned place preference (CPP), neuronal activation, dopamine and its metabolites levels in the nucleus accumbens.

METHODS

Thirty minutes before the ethanol-induced CPP test, mice received saline or biperiden at doses of 1.0, 5.0, or 10.0 mg/kg. The time spent in each compartment was recorded for 15 min. After the CPP protocol, animals were euthanized, and we investigated the activation of the nucleus accumbens by immunohistochemistry for Fos. We also quantified dopamine, homovanillic acid (HVA), and dihydroxyphenylacetic acid (DOPAC) levels in the nucleus accumbens by high-performance liquid chromatography (HPLC). Additionally, the rotarod was employed to evaluate the effects of biperiden on motor coordination.

RESULTS

Biperiden at different doses (1.0, 5.0, and 10.0 mg/kg) blocked the expression of ethanol-induced CPP. These biperiden doses increased the number of Fos-positive cells and the dopamine turnover in the nucleus accumbens. None of the doses affected the motor coordination evaluated by the rotarod.

CONCLUSIONS

Our results show that biperiden can modulate the effect of alcohol reward, and its mechanism of action may involve a change in dopamine and cholinergic mesolimbic neurotransmission.

Molecular and circuit mechanisms regulating cocaine memory

Risk of relapse is a major challenge in the treatment of substance use disorders. Several types of learning and memory mechanisms are involved in substance use and have implications for relapse. Associative memories form between the effects of drugs and the surrounding environmental stimuli, and exposure to these stimuli during abstinence causes stress and triggers drug craving, which can lead to relapse. Understanding the neural underpinnings of how these associations are formed and maintained will inform future advances in treatment practices. A large body of research has expanded our knowledge of how associative memories are acquired and consolidated, how they are updated through reactivation and reconsolidation, and how competing extinction memories are formed. This review will focus on the vast literature examining the mechanisms of cocaine Pavlovian associative memories with an emphasis on the molecular memory mechanisms and circuits involved in the consolidation, reconsolidation, and extinction of these memories. Additional research elucidating the specific signaling pathways, mechanisms of synaptic plasticity, and epigenetic regulation of gene expression in the circuits involved in associative learning will reveal more distinctions between consolidation, reconsolidation, and extinction learning that can be applied to the treatment of substance use disorders.

A threshold model for opposing actions of acetylcholine on reward behavior: Molecular mechanisms and implications for treatment of substance abuse disorders

The cholinergic system plays important roles in both learning and addiction. Medications that modify cholinergic tone can have pronounced effects on behaviors reinforced by natural and drug reinforcers. Importantly, enhancing the action of acetylcholine (ACh) in the nucleus accumbens and ventral tegmental area (VTA) dopamine system can either augment or diminish these behaviors. A threshold model is presented that can explain these seemingly contradictory results. Relatively low levels of ACh rise above a lower threshold, facilitating behaviors supported by drugs or natural reinforcers. Further increases in cholinergic tone that rise above a second upper threshold oppose the same behaviors. Accordingly, cholinesterase inhibitors, or agonists for nicotinic or muscarinic receptors, each have the potential to produce biphasic effects on reward behaviors. Pretreatment with either nicotinic or muscarinic antagonists can block drug- or food- reinforced behavior by maintaining cholinergic tone below its lower threshold. Potential threshold mediators include desensitization of nicotinic receptors and biphasic effects of ACh on the firing of medium spiny neurons. Nicotinic receptors with high- and low- affinity appear to play greater roles in reward enhancement and inhibition, respectively. Cholinergic inhibition of natural and drug rewards may serve as mediators of previously described opponent processes. Future studies should evaluate cholinergic agents across a broader range of doses, and include a variety of reinforced behaviors.

Pharmaceuticals that contain polycyclic hydrocarbon scaffolds

This review comprehensively explores approved pharmaceutical compounds that contain polycyclic scaffolds and the properties that these skeletons convey.

Involvement of insular muscarinic cholinergic receptors in morphine-induced conditioned place preference in rats

RATIONALE

Drug addiction represents a pathological usurpation of neural processes involved in learning and memory. Retrieval of drug-related memories can result in drug craving and relapse. Recently, the insula was identified as part of the neuronal circuit responsible for the processing of drug memory; however, its precise role remains unclear.

OBJECTIVE

To investigate the involvement of insular muscarinic acetylcholine receptors (mAChRs) in the processing of drug memory.

METHOD

The morphine-induced conditioned place preference (CPP) was used to assess drug memory. All rats were first trained with morphine to establish the CPP. Sub-groups of these rats were used for contextual cue-induced CPP reinstatement. Other sub-groups of rats underwent extinction of the CPP, and 5 m/kg morphine was used for priming-induced CPP reinstatement. Microinjection of mAChR antagonists or agonists into the insula was performed prior to the CPP tests in order to evaluate their effect on CPP expression.

RESULTS

Insular microinjections of the nonselective mAChR antagonist, scopolamine, and the M₁ antagonist, pirenzepine, significantly inhibited CPP expression in both contextual cue- and priming-induced CPP reinstatement; the M₁ agonist, MCN-A-343, and the M₄ antagonist, tropicamide, enhanced CPP expression. The M₄ agonist, LY2033298, inhibited CPP expression. The M₂ antagonist, methoctramine, and M₃ antagonist, 4-DAMP, had no effect on CPP expression.

CONCLUSION

Our results demonstrate that insular mAChRs play a role in the processing of drug memory. M₁ and M₄ mAChRs work paradoxically; M₁ activation and M₄ inhibition attenuate the expression of drug memory, while M₁ inhibition and M₄ activation augment the expression of drug memory.

Effects of biperiden on the treatment of cocaine/crack addiction: a randomised, double-blind, placebo-controlled trial

Cocaine use affects approximately 13.4 million people, or 0.3% of the world's population between 15 and 64 years of age. Several authors have described drug addiction as a disease of the brain reward system. Given that the cholinergic system impacts reward mechanisms and drug self-administration, acetylcholine (ACh) might play an important role in the cocaine addiction process. We evaluated the efficacy of biperiden (a cholinergic antagonist) in reducing craving and the amount used, and in increasing compliance with treatment for cocaine/crack addiction. It was a study double-blind, randomised, placebo-controlled, 8-week trial of 111 cocaine or crack addicted male patients between 18 and 50 years old. Two groups were compared: placebo (n=55) or biperiden (n=56) combined with weekly sessions of brief group cognitive-behavioural therapy. The efficacy of treatment was evaluated according to the patients' compliance and several instruments: the Minnesota Cocaine Craving Scale, the Beck Depression and Anxiety Scales and a questionnaire assessing the amount of drug used. All of the patients attended weekly sessions for two months. We analysed the data considering the patients' intention to treat based on our last observation. Of the 56 patients in the biperiden group, 24 completed the treatment (42.8%) compared with only 11 patients in the placebo group (20%), which was a significant difference (p=0.009). Compliance with treatment was 118% higher in the biperiden group, which was also the group that presented a statistically significant reduction in the amount of cocaine/crack use (p<0.001). There was statistically significant difference between the craving score in the biperiden group. Pharmacological blockade of the cholinergic system with biperiden is a promising alternative to treat cocaine/crack addiction, helping patients to reduce the amount used and improving compliance with psychotherapy treatment.