Testosterone Positively Modulates Heroin Self-Administration
Males and females differ significantly in their rates, patterns, and trajectories of drug use and abuse. Significant amounts of research has shown the influence of ovarian hormones on drug self-administration, but very few research studies have examined the effects of testicular hormones on heroin self-administrationâ€”even though epidemiological studies show that men are more likely than women to use heroin and other drugs. This study investigates the effects of androgen hormones on heroin self-administration in male rats. To this end, sexually mature male rats received either a bilateral orchiectomy (GDX) or a sham (SHAM) surgery and were implanted with intravenous catheters for heroin self-administration. Rats were trained to self-administer heroin. In daily test sessions, and heroin self-administration was examined over a 30-fold dose range. We found that GDX rats self-administered significantly less heroin than SHAM rats at all doses tested. These data suggest that testosterone positively modulates heroin self-administration and that androgenic hormones may increase heroin intake in males.