FIGURE 1.

Copulatory pattern of the male rat. The male exhibits a series of mounts and intromissions until achieving ejaculation. During mounting the male lifts his forebody over the female hindquarters, clasping her flanks with its forepaws while keeping its hindlegs on the floor, and begins a series of rapid shallow movements of the pelvis without achieving penetration. Thereafter, the male dismounts the female gently. The intromission is a mount in which the male achieves erection and penetration, after which intravaginal pelvic thrusting is observed, followed by abrupt dismounting while jumping backward. The male usually grooms its genitals. Ejaculation is distinguishable by a longer-lasting intromission during which a deep pelvic thrust is observed that coincides with seminal emission. Thereafter, the male slowly dismounts the female and may elevate its forepaws. Ejaculation signals the end of an ejaculatory series, after which a short period of sexual refractoriness appears, the post-ejaculatory interval, which ends once the male restarts copulation with an intromission, completing a copulatory series. ML, mount latency; IL, intromission latency; EL, ejaculation latency; PEI, post-ejaculatory interval (Larsson, 1956; Sachs and Barfield, 1976; Dewsbury, 1979). Table shows the definition of the specific copulatory parameters utilized in the experimental analysis of male sexual behavior in rats. Created with BioRender.com.