Effect of Muscarinic and Nicotinic Receptor Antagonism on Rat Gastric Motor Activity

Abstract

Background/Aims: Our aim was to investigate whether muscarinic and nicotinic receptors mediate nitric oxide release during motor events in the rat stomach. Methods: Isolated rat stomach volume changes were monitored in an organ bath setup with an intragastric balloon coupled to a barostat and studied in basal conditions and during electrical vagal stimulation (EVS). In conscious rats, the intragastric pressure (IGP) was measured during test meal infusion. Results: In the presence of N^G-nitro-L-arginine methyl ester (L-NAME; 0.1 mmol/l), EVS induced significant gastric contractions (mean ± SEM = 0.27 ± 0.04 ml; n = 6) that could be blocked by atropine (3 µmol/l) and hexamethonium (0.1 mmol/l). In the presence of atropine and/or hexamethonium, EVS-induced relaxations could not be blocked by L-NAME, while exogenous nitric oxide could still relax the stomach. In conscious rats, atropine (1 mg kg^–1) initially decreased IGP, while during further distension it increased IGP. In the presence of L-NAME (30 mg kg^–1) atropine consistently decreased IGP. L-NAME alone significantly increased IGP during the test meal infusion, but this effect was reduced in the presence of atropine. Conclusion: These findings indicate a role for nicotinic and muscarinic receptors in the vagal-stimulation-induced activation of nitrergic nerves in the rat stomach.

Role of Y2 receptors in the regulation of gastric tone in rats

“…We recently described a novel method to assess gastric accommodation in rats by measuring the IGP during nutrient infusion (26,27). Indeed, IGP is determined by the gastric muscle tone, and we demonstrated that increasing or decreasing the gastric tone during food infusion increased or decreased IGP, respectively.…”