Sympathetic control of lower oesophageal sphincter motility in the cat.

Abstract
The action of adrenaline [epinephrine], noradrenaline [norepinephrine] and efferent sympathetic fibers on the smooth muscle of the lower esophageal sphincter (l.o.s.) was studied in vivo on the anesthetized cat and in vitro with the sucrose gap method. Adrenaline and noradrenaline produce a marked depolarization of the circular muscle of the l.o.s. which was suppressed by dihydroergotamine or phentolamine, and greatly reduced by atropine; it remains unaltered by hexamethonium. Sympathetic fibers are excitatory for the l.o.s. They come from the stellate ganglion or run along the splanchnic nerve: the fibers arising from the stellate ganglion (mainly by the cardiac branch of the ganglion) join the vagus nerve at the thoracic level; the fibers running along the splanchnic nerve pass through the celiac ganglion without synapsing; their cellular bodies lie probably in the ganglia of the sympathetic chain. Repetitive stimulation (20-40 Hz) of these fibers induced, with a latency of 5-8 s, a sustained or rhythmic contraction of the l.o.s. This response was suppressed by dihydroergotamine, and greatly reduced by atropine, while hexamethonium had no effect. Stimulation of sympathetic fibers induced facilitation of vagal excitatory responses and inhibited vagal inhibitory responses of the l.o.s. The sympathetic response of the l.o.s. probably resulted from the stimulation of adrenergic receptors which are located on muscular fibers and chiefly on intrinsic neurons. The sympathetic control of the l.o.s. is mainly exerted through cholinergic myenteric neurons which could be excited directly or indirectly by inhibition of inhibitory intrinsic neurones.