Abstract

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Vaginocervical stimulation produces behavioral (induction of sexual receptivity, facilitation of lordosis, immobilization, blockage of flexor withdrawal responses to noxious stimulation, and analgesia), autonomic (increase in heart rate and blood pressure, pupillary dilatation), and neuroendocrine, (reflexive release of oxytocin, luteinizing hormone and prolactin) responses. We now provide evidence of three newly recognized pathways that mediate these responses: 1) a vagus nerve pathway conveying vaginocervical afferent activity directly to the brain, bypassing the spinal cord in rats and women with 'complete' spinal cord injury, producing analgesia and orgasm in the latter; 2) a three-neuron pathway for the Ferguson reflex: pelvic nerve--spinohypothalamic pathway-- paraventricular nucleus--posterior pituitary, using c-fos Fluorogold double-labeling in rats; 3) a five-neuron pathway from cervix to pupil of the eye. In the latter pathway, proceeding from #2) above, the third-order neurons of the paraventricular nucleus project to the thoracic level of the spinal cord where they synapse on sympathetic preganglionic cell bodies. These project to the superior cervical ganglion where they synapse on the post-ganglionics that project directly to the pupil. We present novel evidence that this pathway utilizes oxytocin as the stimulator of spinal cord sympathetic preganglionics.

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Presentation Number SAkomisaruk0535
Keywords: vaginocervical, vagus nerve, orgasm, analgesia, oxytocin