Vaginal and Pelvic Floor Responses to Sexual Stimulation

Vaginal vascular responses to vibratory stimulation of the clitoris, recorded as changes in the amplitude of oscillations of light reflectance at the heart-beat frequency, are: a) very repeatable, b) widespread throughout the vagina but of greater amplitude in its lower anterior wall than elsewhere, c) of very short latency (2–3 sec), but cumulative over 30 sec or more. Such responses are not imitated by raising the abdominal pressure, voluntarily contracting the pelvic floor or the flexors or adductors of the hips, or raising the blood pressure by exercise. They are absent in the foot, hand and rectum when present in the vagina. Sexual fantasy provokes vaginal responses very similar to those from vibratory stimulation of the clitoris, though somewhat less repeatable. Mean vaginal light reflectance, averaged over a cardiac cycle, responds to the same stimuli which affect the amplitude of pulsation. It is, however, much more subject to artifact. Changes in thermal conductivity closely parallel those in amplitude of oscillation of reflectance, with a time-lag which is probably mainly instrumental. Vibratory stimulation of the clitoris causes sustained reflex contraction of the pelvic floor. This reflex (never, it seems, previously described) may be regarded as a tonic counterpart of the well-known phasic bulbocavernosus reflex. The vascular events at and after orgasm and their relationship to features of the pelvic floor electromyogram are described and illustrated; the heart rate falls greatly during the 10 sec after orgasm, the amplitude of vaginal vascular pulsation remains above its prestimulation value for as long as 15 min, and pelvic floor electromyographic activity remains enhanced for at least 2 min.