Short-latency effect of testosterone on copulatory behaviour and ejaculation in sexually experienced intact male rats.

The effect of a single injection of testosterone on the number of stimuli required to trigger ejaculation and on copulatory behaviour was investigated in sexually experienced intact male rats. An intraperitoneal injection of 100 microgram free testosterone 1 h before testing facilitated the copulatory behaviour and decreased the number of mounts and intromissions needed for ejaculation; the latter effect was obtained in a test in which a constant interval was kept between each intromission.