The effects of aromatase inhibition on testosterone-dependent conditioned rhythmic cloacal sphincter movements in male Japanese quail

Abstract

Male Japanese quail produce a foam that, along with semen, is transferred to the quail hen during copulation. This foam has been reported to increase fertility, prolong sperm motility, and enhance sperm competition. Action of the cloacal sphincter muscles in response to visual exposure to a female produces the foam. The rhythmic cloacal sphincter movements (RCSM) responsible for foam production in male quail is elicited by a conditioned stimulus (CS) previously paired with access to a quail hen. These conditioned RCSM are testosterone-dependent. The present experiment was conducted to explore whether, as is the case with most other testosterone-dependent male sexual behaviors in the quail, conditioned RCSM are mediated by the aromatization of testosterone. Castrated, testosterone-treated male quail were presented with paired presentations of an arbitrary focal CS and visual access to a female. Once conditioned RCSM had developed, subjects received twice daily injections of the aromatase inhibitor Vorozole™ (R083842) during a series of extinction test presentations of the CS. Injections of Vorozole™ significantly decreased the number of RCSMs elicited by a sexual CS. This decrease was specific to sexual RCSM; cloacal sphincter movements that occurred following defecation were not affected by Vorozole™. Conditioned sexual RCSM are therefore mediated by the aromatization of testosterone, most likely due to effects on central aromatase activity related to sexual motivation.