NONCONTACT STIMULATION FROM ESTROUS FEMALES EVOKES PENILE ERECTION INRATS

Five experiments demonstrated that noncontact stimulation from estrous females evokes penile erection in a high proportion of sexually exper ienced male rats. In Experiment 1, 23 of 24 males (96%) displayed erec tions while separated from estrous females by a wire-mesh barrier, com pared with 8% when no female was present. In Experiment 2, inaccessibl e estrous females stimulated erection in 100% of males, whereas only 3 8% responded to inaccessible unfamiliar males and 0% to inaccessible p referred food or an empty cage (n = 8/group). These data suggest that nonsexual arousing stimuli do not readily evoke erections. Experiments 3 and 4 demonstrated that bedding collected from estrous females is h ighly attractive to males, but is ineffective in promoting erections e ven when the males can burrow in the bedding. Therefore, estrous odors alone are apparently insufficient to stimulate erection. In Experimen t 5, the percentage of males (n = 18) responding with erection did not vary significantly as a function of their exposure to ovariectomized females (67%), receptive but nonproceptive females (83%), or preceptiv e females (89%), but these stimuli were progressively more effective i n reducing erection latency and increasing the number of erections dis played, suggesting that behavioral cues emitted by females promote ere ction. The display of erection by rats under the conditions used in th ese studies satisfies conventional criteria for recognition as psychog enic erections, which we have provisionally defined as erections that occur without concurrent somesthetic stimulation. The availability of a rodent model of psychogenic erection should foster analysis of its p hysiological mediation.