Depression of postejaculatory ultrasonic vocalization by (+)-bicuculline

The male rat emits ultrasonic (22 kHz) vocalizations after ejaculation and behavioural and electrophysiological evidence suggests that this vocalization reflects an inhibitory state underlying and determining the postejaculatory refractory period (PEI). Present results show that injection into the preoptic-anterior hypothalamic area of (+)-bicuculline methiodide, a GABA antagonist, shortens the PEI and reduces ultrasonic vocalization. It is suggested that the suppression of ultrasonic vocalization following bicuculline treatment reflects a depression of an inhibitory state normally produced by ejaculation.