The role of testosterone in the reward and behavioral responses to cocaine

• Main Author: Minerly, AnaChristina E
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01.01.2005
• Subjects: Psychobiology
• ISBN: 9780542509810; 0542509814

Growing evidence suggests that sex differences in cocaine reward responses are regulated by endogenous gonadal hormones. However, few studies have addressed the role of testosterone on cocaine reward and psychomotor activation. The aim of the present dissertation proposal was to determine whether testosterone influences the development of psychomotor and reward responses to cocaine. The first experiments were conducted with adult rats using chronic and acute methods of testosterone administration. Castrated 8-week old male Fischer rats received placebo or testosterone via SILASTIC capsules (1 to 3 capsules of 100% T) or subcutaneous injections (400, 800, or 1200 μg/kg) concurrent with cocaine administration. While chronic testosterone administration did not alter cocaine-induced conditioned place preference (CPP), concurrent administration of testosterone and cocaine affected the development of cocaine CPP dose-dependently; 400 μg/kg blocked the expression of cocaine-induced CPP. However, testosterone did not affect cocaine-induced locomotor activity. Furthermore, testosterone-saline-treated controls did not develop CPP, suggesting that at these doses, testosterone does not produce rewarding or motor responses. Anabolic steroids are synthetic derivatives of testosterone which have a high abuse potential. Recent finding indicate that anabolic steroid use is becoming increasingly prevalent among adolescents, a population that has previously been associated with cocaine use. Although both substances lead to complex behavioral responses, little is known about the physiological and behavioral effects of testosterone when co-administered with cocaine. As such, subsequent experiments involved studying whether testosterone might differentially affect cocaine-induced locomotor behavior within adolescent and adult male rats. To test this postulate, intact adolescent (4-week old) and adult (8-week old) male Fischer rats were pre-treated with vehicle (sesame oil) or testosterone (5mg/kg or 10 mg/kg) 45 minutes prior to saline or cocaine (20mg/kg) administration. Testosterone was found to differentially affect cocaine-induced locomotor behavior between adult and adolescent male rats. Testosterone did not have an effect at any dose, on ambulations, rearing, or total locomotor counts among adults. However, testosterone decreased both ambulatory and rearing behaviors among adolescents. No effects were found for total locomotor counts. These findings suggest that testosterone may act within the adolescent DA system, thereby altering the response to cocaine.