HISTOCHEMICAL STUDIES ABOUT PARTICIPATION OF M-1 AND M-4 SUBTYPE MUSCARINIC RECEPTORS IN NITRIC OXIDE PATHWAY IN THE GUINEA-PIG GASTRIC FUNDUS

摘要

Nicotinamide adenosine dinucleotide phosphate-diaphorase (NADPH-d) staining after muscarinic receptor activation by (4-Hydroxy-2-butynyl)-1-trimethylamnionium-m-chlorocarbanilate chloride (McN-A-343) in the myenteric neurons of guinea-pig gastric fundus was investigated. The staining intensity of myenteric neurons was evaluated by their optical density (01)) in arbitrary units (AU). After muscarinic activation by McN-A-343 (10 mu M), the OD of NADPH-d neurons in the control group was 81.7 +/- 1.3 AU. Muscarinic activation after blockade of muscarinic M-1 subtype receptors by telenzepine (0.1 mu M) significantly increased the OD of the neurons to 59.0 +/- 1.0 AU. After blockade Of M-4 receptors by tropicamide (0.1 mu M), however, the OD does not change (82.0 +/- 1.1 AU) toward control. These results indicate that the blockade of M, muscarinic receptors potentiates the release of nitric oxide, while M-4 are not involved in modulation of nitrergic neurotransmission.