HORMONAL MODULATION OF EXTINCTION RESPONSES INDUCED BY SEXUAL STEROID-HORMONES IN RATS

A functional interrelation between the nervous and endocrine systems h as been established. However, few studies have dealt with the effects of sexual steroids on learning and memory. The aim of this work was to determine whether sexual steroid hormones could modulate the extincti on response of a passive avoidance conditioning in rats. Male Wistar r ats, randomly assigned to five groups, two controls and three experime ntal groups, were submitted to a one-trial passive avoidance condition ing and tested for their retention 24 hr after and during 10 weeks. On e control group received no treatment at all, the other received veget able oil, and the three experimental received 20 mg of testosterone en anthate, 0.8 mg estradiol valerate, or 4 mg nandrolone decanoate, resp ectively. All substances were applied in a 0.3 ml volume, 24 hours bef ore training and before testing for retention each week during 10 week s. Results indicate that the extinction process is modulated by these hormones, since testosterone and estradiol facilitate extinction, wher eas the anabolic androgen produced a resistance to the extinction proc ess.