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Electrophysiological analysis of responses to intrinsic nerves in circular muscle of opossum esophageal muscle


American Journal of Physiology 254(1 Pt 1): G107-G116
Electrophysiological analysis of responses to intrinsic nerves in circular muscle of opossum esophageal muscle
The nerve-mediated responses to electrical field stimulation (EFS) along the opossum esophageal circular smooth muscle were studied with the sucrose-gap recording technique. Strips from 1-2, 4-5, 7-8, and 10-11 cm above the lower esophageal sphincter were stimulated with short-train (300 ms) and long-train (3 s) durations at 29.degree. C. The response always consisted of a hyperpolarization [inhibitory junction potentials (IJP)] followed by an "off depolarization" often associated with spike potentials and mechanical contraction. Proximal to distal differences in the characteristics of the evoked responses were found, i.e., increasing amplitude, duraiton and time to peak hyperpolarization of the IJP, increasing latency, and amplitude of the off depolarization. Neither atropine, scopolamine, physostigmine, nor guanethidine altered these characteristics substantially, Circular strips of muscularis externa, studied in the organ bath at 37.degree. C using 10-s EFS trains at 5-40 pps, produced off contractions, enhanced by physostigmine and reduced by atropine. High-frequency stimulation occasionally initiated small persistent intrastimulus ("on") responses' some were sensitive to cholingergic agents, but there was no gradient in the delay in their onset. Atropine-insensitive and tetrodotoxin-potentiated transient on responses were occasionally detected. We conclude that only the noncholinergic, nonadrenergic innervation provides a functional intrinsic innervation directly to the oppossum esophagus circular smooth muscle when nerves are activated by EFS.


Accession: 005349401

PMID: 3337229



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