Body surface stimulation and rectal motility

The effects of mechanical stimulation on various skin areas on rectal motility were examined in anesthetized rats as a model of human. The rectal motility was measured by the balloon method at a position about 4–6 cm from the anus. Mechanical stimulation of the perineum induced a characteristic contraction of the rectum. Stimulation of the other skin areas did not produce any responses in the rectal motility. After the spinal transection at the 1st to 2nd cervical level, stimulation on the hindpaw and lower abdomen as well as the perineum induced the characteristic contraction of the rectum. These responses were abolished by severance of the pelvic nerves. After the severance of the sympathetic nerves innervating the rectum, the rectal motility increased its frequency, behind which the stimulation-induced responses were hidden and could not be observed. These results indicate that rectal motility was modulated by cutaneous mechanical stimulation through a segmental spinal reflex mechanism in anesthetized rats.