MECHANISMS REGULATING MALE SEXUAL-BEHAVIOR IN THE RAT - ROLE OF 3-ALPHA-ANDROSTANEDIOL AND 3-BETA-ANDROSTANEDIOL

To assess whether naturally occurring 5 alpha-androstanediols (5 alpha -androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta,17 bet a-diol) play a role in the regulation of male sexual behavior in the r at, their capability to restore copulatory behavior in castrated anima ls was evaluated. Androstanediols were chronically administered either alone or in combination with 5 alpha-dihydrotestosterone (DHT) or wit h estradiol-17 beta (E(2)). Animals treated with testosterone (T), DHT , E(2), and vehicle, either alone or in different combinations, served as controls. The occurrence of mounting, intromission, and ejaculatio n as well as detailed parameters of copulatory behavior were recorded twice per week for 3 weeks. At the end of treatments, the weights of s ex accessory organs were also recorded. When 3 beta,5 alpha-androstane diol (3 alpha-diol; 500 mu g/day) was administered in combination with DHT (300 mu g/day), full copulatory behavior was restored in all subj ects in a manner similar to that obtained with E(2) plus DHT or T plus DHT combinations, thus indicating an estrogen-like behavioral effect of 3 beta-diol. Administration of 3 alpha,5 alpha-androstanediol (3 al pha-diol; 500 mu g/day) combined with DHT also restored sexual behavio r, though to a lesser extent. When 3 alpha-diol (500 mu g/day) was sim ultaneously administered with E(2) (5 mu g/day), the copulatory behavi or of castrated animals was fully restored in a fashion similar to tha t observed after administration of DHT plus E(2) and T plus E(2) combi nations, indicating a potent androgen-like effect of 3 alpha-diol. The behavioral effect of 3 beta-diol plus E(2) was significantly less pot ent. When given alone, each androstanediol only partially restored cop ulatory behavior. Administration of Sol-diol either alone or combined with DHT or E(2) induced a significant increase in ventral prostate an d seminal vesicle weight, mimicking the effects of T and DHT, whereas 3 beta-diol had very little effect. The results suggest that androstan ediols may have a role as synergizing molecules in regulating male sex ual behavior in rodents. The data also provide a possible explanation for the behavioral effects of DHT when given at supraphysiological dos es.