Inhibition of gastric motility via an extraspinal pathway, by afferent mesenteric nerve stimulation in the pitched rat

Calcitonin gene-related peptide and spinal afferents partly mediate postoperative colonic ileus in the rat

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a widely distributed neuropeptide contained in intrinsic and extrinsic neurons of the gastrointestinal wall that has been shown to be released by noxious stimulation, to be involved in nociception, to inhibit gastrointestinal motility, and to partly mediate postoperative gastric ileus. We hypothesized that abdominal surgery-induced release of CGRP might inhibit postoperative colonic motility and food intake.

METHODS

Colonic transit, stool pellet number, stool pellet weight, and food intake were measured for 48 hours after induction of postoperative ileus in rats. CGRP was immunoneutralized by preoperative injection of CGRP monoclonal antibody, or visceral afferent nerve fibers containing CGRP were functionally ablated by topical capsaicin treatment of the vagus nerves or of the celiac/superior mesenteric ganglia before abdominal surgery.

RESULTS

Abdominal surgery increased colonic transit time and decreased 24-hour cumulative stool pellet number, stool pellet weight, and food intake. CGRP immunoneutralization reversed postoperative inhibition of colonic transit, 24-hour cumulative stool pellet number, stool pellet weight, and food intake by 77%, 82%, 80%, and 52%, respectively. Whereas ablation of vagal afferent nerve fibers had no effect, spinal afferent nerve fiber ablation reversed postoperative inhibition of 24-hour cumulative stool pellet number, stool pellet weight, and food intake by 41%, 38%, and 19%, respectively.

CONCLUSIONS

CGRP and spinal afferent nerve fibers partly mediate postoperative colonic ileus and inhibition of food intake in the rat. By the magnitude of reversal of postoperative ileus, CGRP seems to be an important mediator of postoperative colonic ileus. Our results for the first time show involvement of a neuropeptide and spinal afferents in the mediation of postoperative colonic ileus and postoperative inhibition of food intake in rats.

Role of spinal afferents and calcitonin gene-related peptide in the postoperative gastric ileus in anesthetized rats

OBJECTIVE

The object of this study was to investigate the mechanisms of postoperative gastric ileus in an experimental model of abdominal surgery in anesthetized rats.

SUMMARY BACKGROUND DATA

Sensory neurons partly mediate postoperative gastric ileus. Among other neuropeptides, sensory neurons contain calcitonin gene-related peptide (CGRP) and release CGRP in response to noxious stimulation. Because CGRP inhibits gastric motility, it was hypothesized that abdominal surgery stimulates sensory neurons, which then releases CGRP, thereby inhibiting gastric motility.

METHODS

Postoperative ileus was induced by abdominal surgery. Gastric corpus motility was measured by an intragastric catheter. CGRP action was blocked by CGRP immunoneutralization or by a CGRP receptor antagonist. Spinal sensory neurons were ablated by application of a sensory neurotoxin (capsaicin) to the celiac and superior mesenteric ganglia.

RESULTS

Abdominal surgery decreased gastric corpus motility in the first 5 minutes after abdominal surgery by 59 +/- 5% and by 24 +/- 4% during the 1st postoperative hour. Capsaicin pretreatment of the celiac and superior mesenteric ganglia, CGRP immunoneutralization, or CGRP receptor antagonism reversed the postoperative decrease in gastric corpus motility during the 1st postoperative hour by 50%, 100%, and 59%, respectively.

CONCLUSIONS

These data indicate that spinal sensory neurons and CGRP partly mediate postoperative gastric ileus. CGRP may be released from spinal sensory neuron terminals in the celiac and superior mesenteric ganglia as part of an extraspinal intestinogastric inhibitory reflex activated by abdominal surgery.