AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 2 561-R568, Copyright © 1994 by American Physiological Society
Intestinal capsaicin transiently attenuates suppression of sham feeding by oleate
C. S. Tamura and R. C. Ritter
Department of Pharmacology/Toxicology, Washington State University, Pullman 99164.
Intraintestinal infusion of oleic acid reduces food intake in rats and
other mammals. The neural mechanisms that mediate this behavioral response
to intestinal stimulation are incompletely appreciated. We have found that
intraintestinal infusion of capsaicin reduces sham feeding. In addition, 24
h after a single intestinal capsaicin infusion, reduction of sham feeding
by intestinal oleate infusion was attenuated. However, by 48 h
post-capsaicin, suppression of sham feeding by oleate had returned to
pre-capsaicin levels. Repeated intestinal administration of capsaicin
produced less attenuation of oleate-induced suppression of sham feeding,
suggesting the development of tolerance to capsaicin. Unlike systemic
capsaicin, intestinal capsaicin does not impair cholecystokinin-induced
reduction of feeding or the corneal chemosensory reflex. Furthermore, there
are no histochemical signs of vagal sensory degeneration in the hindbrain
after intraintestinal capsaicin. Our results suggest that a
capsaicin-sensitive substrate in or near the intestine is responsible for
mediating the reduction of sham feeding by intestinal oleate infusion.
