Electrically coupled intrinsic responses of feline lower esophageal sphincter

Intraluminal pressures and serosal myoelectric activity were recorded simultaneously from the esophagus, lower esophageal sphincter (LES), and stomach of chloralose-anesthetized cats. The LES demonstrated intermittent spike activity basally without slow waves and was distinct from esophagus and fundus. LES spike activity was not correlated with basal sphincter pressure. Dose-dependent increases in both spikes and pressure occurred with bethanechol, phenylephrine, or pentagastrin. Increased spike activity preceded the onset of the pressure rise and peaked during the rise in pressure. Changes in LES pressure and spike activity following these agents were correlated closely (r = 0.92, P < 0.01). Atropine and isoproterenol inhibited pressure and spike activity similarly. Intrinsic reflexes to endogenous stimuli gave parallel spike and pressure changes. Distal esophageal acidification produced an increase in LES pressure that was correlated with increased spike activity. LES spike activity and pressure were inhibited similarly by antral distension or gastric acidification. Dissection of the distal esophagus from the diaphragm or bilateral cervical vagotomy had no effect on either LES spike activity or pressure. These studies indicate that a) LES myoelectric activity consists of spike discharges that are not correlated to resting pressure, b) abrupt changes in sphincter pressure following either intrinsic reflexes or neurohormonal agents are closely associated with similar changes in spike activity, and c) spike activity and sphincter pressure are intrinsic to the LES.