Male preference for the odors of estrous female mice is enhanced by the neurosteroid 3α-hydroxy-4-pregnen-20-one (3αHP)

Abstract

The effects of the centrally produced allylic neurosteroid, 3α-hydroxy-4-pregnen-20-one (3αHP), on the responses of male mice to the odors of estrous female mice were examined in an odor preference test. Control untreated mice displayed a significant preference for the odors of an estrous female, spending more time in a Y-maze in the vicinity of the odors of an estrous than a non-estrous female. Intracerebroventricular (i.c.v.) administrations of 3αHP enhanced male preference for the odors of estrous females, causing a significant dose-related (0.01–1.0 μg) increase in the amount of time spent in the proximity of the odors of the estrous female, while having no significant effect on the responses to the non-estrous female odors. These effects of 3αHP were stereospecific, with the stereoisomer, 3β-hydroxy-4-pregnen-20-one (3βHP), having no significant effects on odor preferences. The analgesic, morphine, also had no significant effects on the responses to female odors suggesting that the enhanced preference for estrous female odors were unlikely to be directly due to any analgesic effects of 3αHP. The effects of 3αHP were significantly reduced by peripheral administrations of the GABA A antagonists, bicuculline and picrotoxin, but were unaffected by either the benzodiazepine antagonist, Ro 15-1788, or the opiate antagonist, naloxone. These results suggest that the neurosteroid 3αHP has facilitatory effects on olfactory mediated male sexual interest or motivation that involve interactions with the GABA A receptor.