Khare S, Wilson DM, Tien XY, Brasitus TA. M3 muscarinic receptors on rat colonocytes are coupled to particulate guanylate cyclase activation.
BIOCHIMICA ET BIOPHYSICA ACTA 1993;
1179:234-7. [PMID:
8105894 DOI:
10.1016/0167-4889(93)90147-h]
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Abstract
The ability of muscarinic receptor antagonists to compete with (-)-[3H]quinuclidinyl benzilate ([3H]QNB) binding was compared with their ability to block carbachol-mediated stimulation of particulate guanylate cyclase activity in rat colonocytes. The binding of [3H]QNB to membranes was inhibited by antagonists with the following rank order of potencies (inhibitory constants, nM): atropine (2.5) approximately 4-diphenylacetoxy-N-methylpiperidine iodide (4-DAMP) [4.6] >> pirenzepine (121) > methoctramine (385). 4-DAMP (IC50 = approximately 10 nM) was also more potent in blocking carbachol-induced stimulation of guanylate cyclase activity than either pirenzepine (IC50 = approximately 700 nM) or methoctramine (IC50 = approximately 1500 nM).
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