Androgenic and estrogenic control of the self-priming effect of LHRH in the castrated male rat.

Intact pubertal or young adult male rats release more luteinizing hormone in response to luteinizing hormone releasing hormone (LHRH) if pretreated with LHRH than if pretreated with saline. Castrated male rats do not show this self-priming effect of LHRH. In an attempt to determine the testicular factor responsible for the maintenance of the self-priming effect, pubertal male rats were castrated and implanted subcutaneously with various sizes of testosterone-filled Silastic capsules. Control rats were castrated or sham-operated and implanted with empty capsules. Rats were examined for a self-priming effect 4 days later. All sizes of testosterone capsules used maintained the self-priming effect. Three additional experiments were performed to determine the ability of dihydrotestosterone, estradiol and androstenedione to maintain a self-priming effect. The following groups were included in each experiment: castrated plus empty capsule, castrated plus testosterone-filled capsule, castrated plus one of two sizes of capsule filled with the steroid of interest, and sham-operated plus empty capsule. Dihydrotestosterone and estradiol, but not androstenedione were capable of maintaining a self-priming effect. Since it is generally considered that dihydrotestosterone cannot be aromatized to estrogen, this action of estradiol and dihydrotestosterone is probably accomplished by different mechanisms.