Differential Effects of Carbachol and Oxotremorine on Muscarinic Receptors, Cyclic Amp Formation, and Phosphoinositide Turnover in Chick Heart Cells
A central theme in current studies of muscarinic receptors is the definition of muscarinic receptor subtypes. Early evidence for the existence of such receptor subtypes came from studies of physiological responses mediated through muscarinic receptors in various tissues (1, 7). More recently, investigators have used radioligand binding studies to look for muscarinic receptor subtypes. Attempts to distinguish subtypes with classical antagonists have not been fruitful since these agents generally recognize a uniform population of binding sites (9). Several non-classical antagonists such as gallamine (8) and pirenzepine (10) do appear to show selectivety in radioligand binding assays, but gallamine probably acts at a site that is different from the primary antagonist binding site (8) and the selectivity of pirenzepine has been disputed (11).
KeywordsMuscarinic Receptor Cholinergic Agonist Radioligand Binding Assay Muscarinic Receptor Subtype Receptor Binding Property
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