Mounting and brief noncontact exposure of males to receptive females facilitate reflexive erection in rats, even after hypogastric nerve section

In three experiments, reflexive erection in male rats was facilitated by ho using the males for 2 min with inaccessible sexually receptive females. In Experiment 1, males were sexually naive or experienced and received two ref lexive erection tests, 1 week apart, immediately after the males were expos ed to receptive females, to unreceptive females, or to no females (n = 8 pe r group). In both tests, experienced males exposed to estrous females had t he shortest reflexive erection latencies; in Test 1 the differences among g roups were of borderline significance (p = 0.057), but in Test 2 the differ ences among groups were highly reliable (p < 0.01). Further analysis indica ted that only experienced males exposed to receptive females were significa ntly different from other groups. In Experiment 2, sexually experienced mal es (n = 11) received four reflexive erection tests: after being with no fem ale, and 0, 5, or 10 min after exposure to estrous females. As the interval between exposure and test increased, the males had progressively shorter e rection latencies (p < 0.01) and more intense glans erections (p < 0.03). E xperiments 1 and 2 may be viewed as demonstrating the psychogenic facilitat ion of reflexive erections. In Experiment 3, males underwent sham surgery ( sham, n = 10) or bilateral transection of the hypogastric nerves (HgNx, n = 10), which are conventionally viewed as mediating psychogenic erection. Af ter males mounted a receptive female for 5 min without intromission or had 2 min of noncontact exposure to receptive females, the males had shorter er ection latencies (p < 0.001) and more erections (p < 0.02). These facilitat ive effects of pretest stimulation were unaffected by HgN transection. Duri ng copulation tests, HgNx males had longer ejaculation latencies (p < 0.05) and lower intromission ratios (p < 0.05), possible signs of impaired erect ile function. However, in Experiment 4, other males were tested twice for r eflexive erection and copulation after sham (n = 8) or HgNx (n = 9) surgery , and there were no significant effects of surgery on reflexive erection or copulatory behavior. Collectively, these experiments indicate (a) that bri ef noncontact exposure of sexually experienced males to estrous females fac ilitates reflexive erection, (b) that this facilitation increases for at le ast 10 min after the females are removed, and (c) that the hypogastric nerv es do not mediate these facilitative effects. The evidence for a role for t he HgN in copulation was inconclusive. (C) 1998 Elsevier Science Inc.