Lower esophageal sphincter function in the cat: role of central innervation assessed by transient vagal blockade

Publisher Website
Google Scholar
Abstract
Studies were performed on 4 cats to assess the role of extrinsic vagal innervation in the control of lower esophageal sphincter (LES) function. Both cervical vagal nerves were blocked transiently by cooling. LES pressure was measured using a multilumen manometry tube. LES relaxation was assessed during intraesophageal balloon distension in both the striated and smooth muscle portions of the esophagus. Bilateral vagal nerve blockade lowered the mean LES pressure from 58 .+-. 17 to 29 .+-. 9 mm Hg (P < 0.01). During vagal blockade, balloon distension in the striated muscle esophagus further reduced sphincter pressure to 16 .+-. 4 mm Hg (P < 0.01) and that in the smooth muscle esophagus to 15 .+-. 3 mm Hg (P < 0.01). Swallow-induced LES relaxation was abolished during bilateral vagal nerve blockade. During vagal blockade, atropine reduced LES pressure to 10 .+-. 1 mm Hg, phentolamine to 13 .+-. 6 mm Hg and hexamethonium to 10 .+-. 4 mm Hg (all P < 0.01). Normal LES tone in the cat evidently is mediated primarily by 2 separate neural mechanisms: a vagal cholinergic mechanism and a nonvagal mechanism that utilizes both .alpha.-adrenergic and cholinergic receptors; local, intramural mechanisms of high threshold are present in the striated and smooth muscle cat esophagus to allow distention-induced reflex inhibition of the LES; and swallow-induced LES relaxation is dependent on vagally mediated CNS connections.