Activation of an adrenergic and vagally‐mediated NANC pathway in surgery‐induced fundic relaxation in the rat

Abstract

The aim of this study was to pharmacologically characterize and investigate the possible contribution of adrenergic and nonadrenergic noncholinergic (NANC) pathways involved in the relaxation of the rat gastric fundus following abdominal surgery. Using an intragastric balloon, the effect of skin incision (SI), laparotomy (LT) and manipulation of the small intestine followed by caecal resection (M + R) on fundic pressure was evaluated. SI resulted in a brief relaxation of the gastric fundus abolished by guanethidine and blocked by hexamethonium and the combination of phentolamine, propranolol and atropine (PPA). LT induced a longer lasting relaxation which was abolished by guanethidine and hexamethonium. It was blocked by PPA and the combination of ganglionectomy and vagotomy, but unaffected by atropine, vagotomy or ganglionectomy. M + R induced a long-lasting relaxation which was only partly blocked by guanethidine or PPA, illustrating an inhibitory NANC component. Vagotomy combined with guanethidine completely abolished the relaxation following M + R, whereas it was significantly blocked by hexamethonium and the combination of ganglionectomy with vagotomy. These results indicate that SI, LT and M + R induce inhibition of fundic motility via an adrenergic mechanism. During M + R, an additional vagally mediated inhibitory NANC pathway is activated. Finally, we suggest that LT and M + R inhibit the gastric fundus via both a splanchnic and a vagal reflex pathway.