Effect of galanin on the opossum lower esophageal sphincter.

The objective of this investigation was to examine the effect of galanin on the resting tone and neurally mediated relaxation of the lower esophageal sphincter (LES) in anesthetized opossums. Galanin caused a dose-dependent rise in the sphincter pressure when given either intra-arterially or intravenously. The D50 of intra-arterial galanin was 1.OX10(-11) mols/kg. The rise in the sphincter pressure caused by galanin was not modified by atropine, phentolamine, methysergide, pyrilamine or indomethacin. Furthermore, the contractile response of galanin on the LES was also not affected by tetrodotoxin. The fall in the sphincter pressure in response to vagal efferent stimulation, intramural stimulation or esophageal distension was antagonized by galanin. The results of these studies suggest that, 1) galanin causes sphincter contraction by its direct action on the smooth muscle, and 2) galanin suppresses LES relaxation. These studies suggest that galanin may be an important neuropeptide for the modulation of resting tone and LES relaxation.