Descending peristaltic reflex in the opossum esophagus.
Paterson, W. G., B. Indrakrishnan.
Gastrointestinal Diseases Research Unit, and Departments of
Medicine and Physiology, Queen's University, Kingston, Ontario,
Canada
APStracts 2:0064G, 1995.
To test the hypothesis that the distention-induced esophageal
peristaltic reflex involves a polysynaptic pathway, a triple organ
bath was used to chemically isolate different regions of the opossum
smooth muscle esophagus while leaving in continuity the intramural
neuromuscular apparatus. Balloon distention in the oral chamber
evoked membrane hyperpolarization in the aboral chamber which was
followed, upon balloon deflation, by depolarization, spike burst and
circular smooth muscle contraction. This reflex was abolished by
adding tetrototoxin to any of the chambers. Addition of Ca++-free, 20
mM Mg++ Krebs' solution (to block synaptic transmission) to the
intermediate chamber did not affect the descending peristaltic
reflex. However, Ca++-free, 20 mM Mg++ Krebs' solution markedly
attenuated the reflex when placed in either the oral or the aboral
chamber. Furthermore, the nitric oxide synthase inhibitor L-NAME,
when placed in the aboral chamber, abolished the reflex. Other
putative neurotransmitter antagonists were without effect when placed
in any chamber. These studies suggest that the intramural neural
pathway which mediates the descending peristaltic reflex in the
opossum esophagus is not polysynaptic, but rather involves long
descending neurons which depend on nitric oxide as a final mediator.
Received 18 October 1994; accepted in final form 16 March 1995.
APS Manuscript Number G420-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.