The effects of p-chloromercuribenzoate on muscarinic receptors in the cerebral cortex

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Abstract
1 The action of p-chloromercuribenzoate (PCMB) on the ligand binding properties of the muscarinic receptors in the rat cerebral cortex has been examined. 2 At low concentrations, PCMB produces a selective change in the binding of agonists without any effect on the binding of antagonists. 3 At higher concentrations, the structure-binding profile for binding antagonists is changed. The affinity of agonists is greatly reduced and the heterogeneity of binding eliminated. 4 The effects of both high and low concentrations of PCMB can be reversed by dithiothreitol. 5 Inactivation of receptors proceeds in parallel and is kinetically complex. It can only be partially reversed by dithiothreitol. 6 Evidence is presented connecting the low affinity agonist binding site with the high affinity pirenzepine binding site. 7 The changes produced by PCMB have been interpreted in terms of the modification of receptor conformation.