Evidence that probing the vaginal cervix is analgesic in rats, using an operant paradigm.

Probing against the vaginal cervix (CP) suppresses responses to noxious stimulation in rats. The first experiment rules out the possibility that this effect is due to CP-induced immobilization. All rats first learned to press a panel, thus terminating noxious skin shock. Then they either received CP (experimentals) or did not (controls) when they pressed the panel during skin shock that was inescapable. The controls soon showed extinction of the panel-press response, whereas the experimentals continued pressing the panel and obtaining CP, for significantly more trials. The rats thus performed an operant response for CP at a time before CP could have blocked their movement. The second experiment argues against the possiblity that CP exerts its effect by "distracting" the rats from the skin shock. The rats received inescapable skin shock which continued for 7 sec after each panel-press response. During this shock one group received CP, and another received perineal probing ("distraction" control). The panel-press latency was significantly shorter in the CP group than in the perineal group. Latency in a control group, in which shock was terminated as soon as the rats pressed the panel, did not differ significantly from the CP group. Latency in another control group, in which the shock persisted for 7 sec after the rats pressed the panel with no probing being applied, was not significantly different from that of the perineal-probing group but was significantly longer than latency in the CP group. Thus the present studies suggest that CP is indeed analgesic and that this effect of CP is mediated by neither movement inhibition nor distraction.     

Gender Differences in Healthcare Utilization: The Mediating Effect of Utilization Propensity

To evaluate the mediating effect of utilization propensity (UP) on gender differences in healthcare utilization (HCU), a representative sample of the German general population (N = 2,510) was assessed with questionnaires. Gender differences in HCU, UP, and the mediating effect of UP were investigated using regression analyses. UP was significantly associated with HCU. The explanatory power of gender for UP, and of UP for HCU was prevailingly weak. UP had a mediating effect on gender differences in HCU, but the effect was very small. This is partly attributable to common problems in the prediction of behavior by attitudes and the operationalization of UP.     

Vaginal stimulation in rats induces prolonged lordosis responsiveness and sexual receptivity.

Sexual receptivity to males resulted from stimulation of the vagina with a glass rod in previously unreceptive ovariectomized, estrogen-treated rats. Several minutes of rejection behavior preceded the receptivity. In a second study, manual palpation was used to determine the duration of the lordosis response facilitation. Initially, all females were unresponsive to manual flank-perineum stimulation (palpation). Vaginal stimulation plus palpation, which together elicit lordosis, facilitated subsequent lordosis responses to palpation. This effect persisted for several hours after the vaginal stimulation was applied. Vaginal stimulation alone, which was ineffective in eliciting lordosis, also facilitated lordosis in response to subsequent palpation. Repeated palpation did not facilitate lordosis. These prolonged effects were independent of hormone treatment.     

Medial preoptic area and onset of maternal behavior in the rat.

The present series of experiments examined whether the medial preoptic area (MPOA) is involved in the onset of maternal behavior in the rat. Previously, the MPOA had been shown to be important in the maintenance of maternal behavior in the lactating rat. The first experiment investigated whether estradiol benzoate (EB) acts on the MPOA to facilitate the onset of maternal behavior in the 16-day pregnant, hysterectomized, and ovariectomized female rat. Such rats when given EB implants in the MPOA had significantly shorter latencies for the onset of maternal behavior than had females implanted with cholesterol in the MPOA or with EB in the ventromedial hypothalamus, in mammillary bodies, or under the skin. A second experiment showed that estrogen-induced prolactin release was not involved in this facilitation. A third experiment indicated that MPOA lesions disrupt the onset of maternal behavior that is induced by pup stimulation in virgin females. It was concluded that the MPOA is involved not only in the maintenance of maternal behavior but in the hormonally mediated onset of maternal behavior and the onset of maternal behavior induced in virgin females by pup stimulation.     

Neural pathways mediating vaginal function: the vagus nerves and spinal cord oxytocin

The initial observations, made in our laboratory with Knut Larsson, of the ability of vaginocervical stimulation (VCS) to block withdrawal responses to foot pinch in rats has led to findings of multiple behavioral, autonomic, and neuroendocrine effects of this potent stimulus in rats and also in women. It has led to an understanding of: (1) the neuroanatomical and neurochemical basis of a novel and potent pain-blocking mechanism; (2) likely neuroanatomical pathways mediating both the Ferguson reflex and a specific autonomic response - the pupil-dilating effect of VCS; (3) a role for oxytocin as a putative central nervous system neurotransmitter that stimulates autonomic sympathetic preganglionic neurons within the spinal cord; and (4) a novel pathway that can convey sensory activity from the cervix, adequate to induce orgasm, via the vagus nerves. This latter pathway bypasses the spinal cord and projects directly to the medulla oblongata, and thus can convey genital afferent activity despite complete spinal cord injury at any level.