Inhibitory centers in sexual behavior in the male rat.

Small lesions placed near the diencephalic, mesencephalic junction, in either the lateral or medial mammillary region, resulted in an increase of copulatory behavior. This increase was expressed both by increased numbers of copulation plugs formed per 14-day interval and by increased percentage of days on which copulation occurred. Inhibitory structures thus form an essential part of the circuitry involved in mediation of sex behavior in the male.