Capsaicin-sensitive afferent nerves activate submucosal
secretomotor neurons in the guinea pig ileum.
Vanner, S., Macnaughton, W. K.
Depts. of Physiology and Medicine, Queen's University, Kingston,
Ontario, Canada, Defence Research Establishment Ottawa and Dept. of
Physiology, University of Ottawa, Ottawa, Canada.
APStracts 2:0051G, 1995.
This study examined whether capsaicin-sensitive sensory nerves
regulate intestinal ion transport using both Ussing chamber and
intracellular recording techniques in in vitro submucosal
preparations from the guinea pig ileum. In Ussing chamber studies,
serosal application of capsaicin (20 nM-20[mu]M) evoked a biphasic
dose-dependent increase in short circuit current (Isc)(EC100-200nM,
2[mu]M respectively). In chloride free buffer, capsaicin responses
were significantly reduced. Capsaicin evoked little or no response
when extrinsic sensory nerve fibers had been surgically removed and
tetrodotoxin and low calcium and high magnesium solutions blocked
responses to capsaicin. In epithelial preparations, devoid of
submucosal neurons, capsaicin had virtually no effect suggesting that
responses evoked by capsaicin-sensitive nerves result from activation
of submucosal secretomotor neurons. Intracellular recordings from
single submucosal neurons demonstrated that capsaicin (2[mu]M)
superfusion depolarized neurons with an associated decreased
conductance. Depolarizations were completely desensitized when
capsaicin was reapplied but synaptic inputs were unaffected. This
study suggests that capsaicin-sensitive nerves can regulate ion
transport in the gastrointestinal tract by release of
neurotransmitter(s) which activate submucosal secretomotor neurons.
Received 7 September 1994; accepted in final form 8 March 1995.
APS Manuscript Number G337-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 March 1995.