ORAL-PHARYNGEAL-ESOPHAGEAL AND GASTRIC CUES CONTRIBUTE TO MEAL-INDUCED C-FOS EXPRESSION

We recently demonstrated that a meal induces c-fos immunoreactivity in the dorsal motor nucleus of the vagus (DMV), the nucleus of the tract us solitarius (NTS), and the area postrema (AP) of the rat brain stem. This response was not eliminated by the cholecystokinin A (CCK-A) ant agonist L-364,718, a finding suggesting that feeding induces c-fos imm unoreactivity by a pathway that is largely independent of CCK-A recept or activation. Consequently, the role of alternative gastrointestinal cues in the induction of c-fos was investigated. The induction of c-fo s 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 d egree of staining in the more rostral section of NTS examined as fistu la-closed and fed rats, but fewer c-fos-positive nuclei in the more ca udal level of the NTS. The potential for gastric distension to induce c-fos was assessed after the inflation of a gastric balloon. Physiolog ical inflation of the balloon produced marked c-fos induction primaril y in the medial NTS.