Vagovagal reflex motility patterns of the rat esophagus

Esophageal reflex motility and its neural correlates were investigated in 94 urethan-anesthetized adult male albino rats. When distended by means of a stationary balloon, the cervical and thoracic esophageal portion responded with a single pressure wave (type I response), whereas the diaphragmatic (intercrural) segment exhibited rhythmic contractions (type II response). Balloon deflation resulted in an off response aboral to the balloon. Bilateral cervical vagotomy or systemic D-tubocurarine abolished all types of reflex responses. Both type I and type II responses were associated with multiunit discharges in the central subnucleus of the solitary tract complex (NTSC) and the compact formation of the nucleus ambiguus (AMBC). Type I discharges, consisting of single bursts, and type II discharges, consisting of rhythmic 0.6-Hz bursts, preceded intraesophageal pressure waves in a fixed phase relationship, persisted after contralateral vagotomy, and were eliminated by ipsilateral vagotomy. During neuromuscular paralysis, peak intraburst discharge rates were reduced in both the NTSC and AMBC, with a concomitant decrease in rhythmicity. It is concluded that bolusevoked peristalsis of the rat esophagus is 1) segmentally organized; 2) effected by a bilateral uncrossed reflex arc consisting of vagal viscerosensory, NTSC premotor, and AMBC motoneurons innervating the striated muscle tunic and 3) strongly facilitated by reafferent feedback.