Activation of sexual reflexes of male rats by dihydrotestosterone but not estrogen.

Previous studies have shown that withdrawal and administration of testosterone propionate (TP) has a quantitative influence on sexual reflexes which parallels changes in copulatory activity following castration and administration of TP. The present study involving castrated spinal male rats explored further this parallel, focusing on the effects on sexual reflexes of the administration of dihydrotestosterone propionate (DHTP) and estradiol benzoate (EB), both of which can activate sexual behavior in spinally intact castrated male rats, but only if given in very large doses for a prolonged period of time. A parallel effect on reflexes and behavior was not found inasmuch as DHTP activated sexual reflexes at a dose (200 microgram daily) considerably below that needed to activate behavior, and EB did not appreciably activate reflexes, even after prolonged treatment at levels (100-200 microgram) higher than necessary to activate behavior. The results, with EB in particular, point out that the display of intromissive and ejaculatory patterns in rats may not involve spinal neural mechanisms that are customarily associated with these behavioral patterns.