THE EFFECTS OF 5 ALPHA-ANDROSTAN-17B-OL-3-ONE (DIHYDROTESTOSTERONE) ON MALE REPRODUCTIVE PHYSIOLOGY AND BEHAVIOR (AROMATIZATION, ANDROGENS)
Abstract
This thesis contains three experiments examining the ability of the nonaromatizable androgen, dihydrotestosterone (DHT), to stimulate sexual behavior and target tissue in male rats and guinea pigs. In Experiment 1, subdermal implantation of silastic capsules filled with DHT maintained the epididymal tissues of castrated rats and guinea pigs. Despite these similar physiological effects, DHT treatment had markedly different behavioral consequences in these two species. Capsules containing sufficient DHT to maintain peripheral structures effectively stimulated mating in castrated guinea pigs, but not in the similarly treated rats. Although the mechanism for the species difference noted in Experiment 1 is unknown, it is possible that reduced bioavailability of DHT to the brain may contribute to its ineffectiveness in rats, since exogenous DHT is metabolized rapidly by male rats. Experiment 2 was designed to bypass potential problems of biotransport by directly stimulating the medial preoptic area with DHT. As was found in Experiment 1, subdermally placed silastic capsules of DHT had no significant effects on the reproductive behavior of castrated rats. However, supplementing peripheral DHT with central implants of testosterone, estradiol, or DHT significantly increased male sexual behavior. These findings suggest that the relative ineffectiveness of peripheral DHT in male rats may be caused by decreased bioavailability of this hormone to the brain regions necessary for the expression of mating behavior. Even though peripheral treatment with DHT is sufficient to stimulate sexual behavior in castrated guinea pigs, there is as yet no direct evidence that the effects of DHT in the guinea pig are due to androgenic stimulation of the brain. In Experiment 3, central implants of DHT, but not comparable cannulae placed in the periphery, significantly increased the mating behavior of male guinea pigs. These data indicate that androgenic stimulation of the guinea pig brain is sufficient to stimulate reproductive behavior in that species. Taken together, the findings that DHT can act centrally to stimulate mating in both rats and guinea pigs are consistent with the possibility that similar hormonal mechanisms influence male sexual behavior in these two species.
Degree
Ph.D.
Subject Area
Psychobiology|Anatomy & physiology|Animals
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