Mechanisms of reflexes induced by esophageal distension

We investigated the mechanisms of esophageal distension-induced reflexes in decerebrate cats. Slow air esophageal distension activated esophago-upper esophageal sphincter (UES) contractile reflex (EUCR) and secondary peristal sis (2P). Rapid air distension activated esophago-UES relaxation reflex (EU RR), esophago-glottal closure reflex (EGCR), esophago-hyoid distraction ref lex (EHDR), and esophago-esophagus contraction reflex (EECR). Longitudinal esophageal stretch did not activate these reflexes. Magnitude and timing of EUCR were related to 2P but not injected air volume. Cervical esophagus tr ansection did not affect the threshold of any reflex. Bolus diversion preve nted swallow-related esophageal peristalsis. Lidocaine or capsaicin esophag eal perfusion, esophageal mucosal layer removal, or intravenous baclofen bl ocked or inhibited EURR, EGCR, EHDR, and EECR but not EUCR or 2P. Thoracic vagotomy blocked all reflexes. These six reflexes can be activated by esoph ageal distension, and they occur in two sets depending on inflation rate ra ther than volume. EUCR was independent of 2P, but 2P activated EUCR; theref ore, EUCR may help prevent reflux during peristalsis. All esophageal perist alsis may be secondary to esophageal stimulation in the cat. EURR, EHDR, EG CR, and EECR may contribute to belching and are probably mediated by capsai cin-sensitive, rapidly adapting mucosal mechanoreceptors. GABA-B receptors also inhibit these reflexes. EUCR and 2P are probably mediated by slowly ad apting muscular mechanoreceptors. All six reflexes are mediated by vagal af ferent fibers.