Effect of bethanechol or vagal nerve stimulation on ileocecal sphincter pressure in the cat

Ileocecal sphincter pressure was studied in the cat, using an open-tipped perfused catheter system. Ileocecal sphincter pressure was measured under basal conditions and in response to bethanechol or direct vagal nerve electrical stimulation. The pressure was 26.1 ± 5.0 mmHg basally, and was unaltered by section of either or both cervical vagi (p > 0.05). Peripheral cervical vagal stimulation gave a 9.1 ± 1.1-mmHg increase in ileocecal sphincter pressure (p < 0.05) but central stimulation had no effect on ileocecal sphincter pressure. The ileocecal sphincter response to peripheral vagal nerve stimulation was antagonized completely by atropine or hexamethonium but not by propranolol or phentolamine. Bethanechol gave a dose-response increase in ileocecal sphincter pressure with a maximal response of 18.0 ± 2.9 mmHg at 50.0 μg/kg (p < 0.01). The ileocecal sphincter relaxed with ileal distension and contracted with colonic distension. These studies indicate that: (a) the ileocecal sphincter shows an excitatory response to vagal stimulation and cholinergic agonists; (b) basal ileocecal sphincter pressure is independent of the vagi; and (c) ileocecal sphincter inhibition can be initiated by ileal distension but not by vagal stimulation.