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.