Courtship ultrasonic vocalizations in male Swiss-Webster mice: effects of hormones and sexual experience.

The effects of testosterone and its metabolites (estradiol and 5 alpha-dihydrotestosterone) on male mouse ultrasonic vocalizations were investigated using Swiss-Webster mice. In the first experiment daily treatment with 50 micrograms or 200 micrograms of testosterone propionate (TP) restored ultrasonic calling in castrated sexually naive males. Treatment with 200 micrograms of dihydrotestosterone propionate (DHTP) also activated ultrasound production, but treatment with 50 micrograms of DHTP or estradiol benzoate (EB 0.5 microgram and 2 micrograms/day) failed to have a significant effect on this measure. In experiment two, the animals used had shown male sexual behavior before castration. These sexually experienced males showed a marked reduction in ultrasound production after castration but significantly increased ultrasound production after daily treatment with either TP (50 micrograms or 200 micrograms), DHTP (50 micrograms or 200 micrograms) or 2 micrograms of EB. Hormones that facilitated ultrasound calling also activated other components of male sexual behavior in this and previous studies with Swiss-Webster mice. The results indicate that hormone dose and precastration sexual experience interact to determine the effects of postcastration treatment on male vocalizations.