The 20-min rate of gastric emptying of a noncaloric solution and c-fos expression detected by immunohistochemistry in the brain were monitored 3 h after abdominal surgery performed under 10-min enflurane anesthesia in rats. Abdominal surgery (laparotomy and 1-min manipulation of the cecum) decreased gastric emptying from 60.8 +/- 3.4 to 25.9 +/- 3.4%. Capsaicin applied to the celiac/superior mesenteric ganglia 2 wk before the experiment reduced the delay in gastric emptying induced by abdominal surgery (46.3 +/- 3.4%), whereas perivagal capsaicin application had no effect (23.6 +/- 7.9%). The corticotropin-releasing factor (CRF) antagonist [D-Phe12, Nle21,38,C alpha MeLeu37]CRF-(12--41) injected intracisternally (10-20 micrograms) prevented postoperative gastroparesis induced by surgery, while having no effect on basal gastric emptying. Abdominal surgery increased the number of Fos-positive cells in brain nuclei regulating autonomic outflow: the nucleus of the solitary tract, locus ceruleus, paraventricular nucleus, and supraoptic nucleus of the hypothalamus. These data indicate that capsaicin-sensitive splanchnic afferent fibers and activation of CRF receptors in the brain are part of the neuronal circuitry mediating gastric stasis 3 h after abdominal surgery.

The role of peripheral corticotropin-releasing factor (CRF) and afferent pathways in mediating abdominal surgery-induced delayed gastric emptying was investigated using an intravenous injection of the competitive CRF antagonist alpha-helical CRF9-41 and capsaicin pretreatment in adult fasted rats. Gastric emptying of a non-caloric solution was measured by the phenol red method. Intravenous CRF (0.13 nmol) inhibited by 65% gastric emptying. CRF effect was completely reversed by simultaneous intravenous injection of alpha-helical CRF9-41 (13 nmol). Abdominal surgery under enflurane anesthesia inhibited gastric emptying by 60% measured 3 h postoperatively. Enflurane anesthesia alone had no effect on gastric emptying 3 h after exposure. Abdominal surgery-induced delay of gastric emptying was reversed by 46, 60, and 100% by capsaicin pretreatment (125 mg/kg, -3 wk), intravenous injection of alpha-helical CRF9-41 (13 nmol), and combined pretreatments with capsaicin and CRF antagonist, respectively. Capsaicin and alpha-helical CRF9-41 given alone or in combination did not influence gastric emptying. These results indicate that peripheral CRF receptors along with capsaicin-sensitive afferent neurons contribute to somatovisceral stress (abdominal surgery)-induced delayed gastric emptying.

Endoluminal release of serotonin (5-HT), substance P (SP), and motilin was quantitated after thoracic vagal nerve stimulation in the cat. In duodenum and jejunum, simultaneous release of these compounds was observed. In contrast, vagal stimulation did not augment the rate of luminal secretion of either 5-HT or SP in the distal ileum. Immunohistochemical studies demonstrated 5-HT in both enterochromaffin (EC) cells and nerves throughout the small bowel. However, we were unable to visualize any SP-containing EC cells in the cat, which suggests that the source of luminal SP in this species must be intramural nerves.

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