AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 1 223-R230, Copyright © 1995 by American Physiological Society
Oral-pharyngeal-esophageal and gastric cues contribute to meal-induced c-fos expression
K. A. Fraser, E. Raizada and J. S. Davison
Department of Medical Physiology, University of Calgary, Alberta, Canada.
We recently demonstrated that a meal induces c-fos immunoreactivity in the
dorsal motor nucleus of the vagus (DMV), the nucleus of the tractus
solitarius (NTS), and the area postrema (AP) of the rat brain stem. This
response was not eliminated by the cholecystokinin A (CCK-A) antagonist
L-364,718, a finding suggesting that feeding induces c-fos immunoreactivity
by a pathway that is largely independent of CCK-A receptor activation.
Consequently, the role of alternative gastrointestinal cues in the
induction of c-fos was investigated. The induction of c-fos after
oral-pharyngeal and esophageal stimuli was examined by use of a
sham-feeding procedure via a gastric fistula. Gastric fistula-closed and
fed rats displayed c-fos immunoreactivity similar to that of meal-fed rats
seen previously. Fistula-open and fed rats showed the same degree of
staining in the more rostral section of NTS examined as fistula-closed and
fed rats, but fewer c-fos-positive nuclei in the more caudal level of the
NTS. The potential for gastric distension to induce c-fos was assessed
after the inflation of a gastric balloon. Physiological inflation of the
balloon produced marked c-fos induction primarily in the medial NTS.
