The GABA B receptor positive allosteric modulator ASP8062 reduces operant alcohol self-administration in male and female Sprague Dawley rats

Rationale Pre-clinical evidence implicates the GABAergic system in mediating the reinforcing effects of alcohol and offers a therapeutic target for alcohol use disorder (AUD). The orthosteric GABA B receptor agonist baclofen decreases alcohol self-administration in animals and alcohol use in humans; however side effects limit its utility. Pre-clinical evidence shows positive allosteric GABA B receptor modulators also decrease alcohol self-administration without untoward side effects. Objectives We assessed the impact of the novel GABA B -positive allosteric modulator ASP8062 and baclofen on operant alcohol self-administration and their potential non-specific effects. Methods The effects of ASP8062 (1 − 10 mg/kg, PO) and baclofen (0.3 − 3 mg/kg, IP) were evaluated in male and female rats lever pressing for alcohol (10%, w/v) under a fixed ratio 2 schedule of reinforcement. On the fourth consecutive day of vehicle, ASP8062 or baclofen administration, active and inactive lever presses, reinforcers earned, head entries, and estimated alcohol consumed were analyzed. Locomotor activity was assessed in separate groups of rats following dosing. Results Both ASP8062 and baclofen decreased alcohol self-administration and amount consumed (g/kg) in male and female rats. ASP8062 decreased operant alcohol self-administration to a greater extent in male rats, whereas baclofen was more efficacious in female rats. ASP8062 did not alter locomotor activity in either sex, whereas baclofen (3.0 mg/kg) decreased activity in male rats yet (1.0 mg/kg) increased activity in female rats. Conclusions ASP8062 decreases alcohol reinforcement like baclofen but without non-specific effects which are influenced by sex. Results support further development of ASP8062 as a potential treatment for AUD in humans.