Colonic mechanosensory afferent input to neurons in the mouse
superior mesenteric ganglion.
Miller, Steven M., and Joseph H. Szurszewski.
Department of Physiology and Biophysics, Mayo Clinic and Mayo
Foundation, Rochester, MN 55905, U.S.A.
APStracts 3:0194G, 1996.
Electrical activity and synaptic responses were recorded
intracellularly in 415 neurons of the mouse superior mesenteric
ganglion (SMG) attached to a segment of distal colon in vitro.
Eighty-seven percent of neurons tested received ongoing nicotinic
cholinergic fast excitatory synaptic potentials (fast EPSPs). Colonic
distension caused an initial transient followed by a sustained,
slowly adapting increase in fast-EPSP activity. Application of
hexamethonium only to the colon reduced, but did not completely
abolish, distension-evoked responses suggesting direct projection of
some distension-sensitive fibers. Ongoing fast EPSPs were abolished
when nerve trunks connecting the SMG to the colon were transected or
blocked with tetrodotoxin applied to the colon. Intracellular
labeling with horseradish peroxidase or Lucifer Yellow revealed that
about 90% of neurons receiving colonic synaptic input had a caudally
projecting axon; about 60% that did not receive colonic input had a
rostrally projecting axon. The latter neurons were found only in the
cephalad ganglion region. These results show that mouse SMG neurons
receive colonic mechanosensory afferent synaptic input and thus may
participate in sympathetic intestinal reflexes.
Received 31 May 1996; accepted in final form 30 August 1996.
APS Manuscript Number G219-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996