Abstract

Drug addiction is characterized by recurring episodes of relapse and has a profound impact on individuals’ well-being as well as our economic and healthcare systems. Although many efforts have been put into developing solutions to treat drug addiction, an effective long-term treatment has yet to be found. Previous animal studies indicate that exogenous oxytocin (OXT) holds potential to treat and reduce relapse, withdrawal and help drug cessation. More particularly, a decrease in psychostimulant drugs (e.g., cocaine and methamphetamine) consumption has been noted while earlier studies also suggested a similar role for OXT in opiate drugs (e.g., morphine and heroin) reward and withdrawal.
In light of those studies, our objective was to continue investigating the role of OXT in inhibiting heroin self-administration (SA) as well as attenuating relapse by using an animal model of stress-induced reinstatement. We examined the effects of acute and chronic administrations of OXT on heroin SA and the reinstatement of extinguished heroin seeking in male rats. Rats were tested under fixed-interval 20 s (FI-20 s) and progressive-ratio (PR) schedules of reinforcement in order to assess heroin intake. Results suggest that OXT did not attenuate heroin taking during the SA sessions under various schedules of reinforcement. Next, we tested the effect of OXT on stress-induced reinstatement of extinguished heroin seeking, by using yohimbine (YOH) as our pharmacological stressor. Contrary to our expectations, central administration of OXT did not attenuate yohimbine-induced reinstatement. In conclusion, contrary to recent findings with psychostimulant drug-trained rats and earlier reports with heroin-trained rats, OXT did not attenuate either heroin SA or yohimbine-induced heroin seeking.