Exploring sex differences in the prevention of ethanol drinking by naltrexone in dependent rats during abstinence

Abstract Background Despite considerable efforts, few drugs are available for the treatment of alcohol (ethanol [EtOH]) use disorders (AUDs). Ethanol directly or indirectly modulates several aspects of the central nervous system, including neurotransmitter/neuromodulator systems. Relapse vulnerability is a challenge for the treatment of EtOH addiction. Ethanol withdrawal symptoms create motivational states that lead to compulsive EtOH drinking and relapse even after long periods of abstinence. Among the therapeutics to treat AUDs, naltrexone (NTX) is a pharmacological treatment for relapse. The goal of the present study was to evaluate the effect of NTX on EtOH drinking in EtOH-dependent male and female rats during abstinence. Methods Wistar rats (males and females) were first trained to orally self-administer 10% EtOH. Half of them were then made dependent by chronic intermittent EtOH (CIE) vapor exposure, and the other half were exposed to air. Using this model, rats exhibit somatic and motivational signs of withdrawal. At the end of EtOH vapor (or air) exposure, the rats were tested for the effects of NTX (10 mg/kg, p.o.) on EtOH self-administration at three abstinence time points: acute abstinence (8 h, A-Abst), late abstinence (2 weeks, L-Abst), and protracted abstinence (6 weeks, P-Abst). Results NTX decreased EtOH intake in nondependent rats, regardless of sex and abstinence time point. In post-dependent rats, the effects of NTX improved with a longer abstinence time (i.e., L-Abst and P-Abst) in males, whereas it similarly reduced EtOH drinking in females at all abstinence points. Conclusions The data suggest that the therapeutic efficacy of NTX depends on the time of intervention during abstinence and sex. The data further suggest that EtOH dependence induces different neuroadaptations in male and female rats, reflected by differential effects of NTX. The results underscore the significance of considering the duration of EtOH abstinence and sex for the development of pharmacotherapeutic treatments for AUD.