Biochemical characterization of muscarinic receptors.

Characteristics of the binding mechanism to specific muscarinic sites were determined by means of high affinity binding of tritium labeled N-methyl-4-piperidylbenzilate (4-NMPB) to homogenate from various regions of mouse brain: cortex, caudate putamen, thalamus, hippocampus, medulla pons and cerebellum. In vivo experiments confirm results obtained when investigating regional distribution of the muscarinic receptors in vitro. Kinetics as well as equilibrium analysis of the binding in the different brain regions to probe the nature of the binding is described. The combined data strongly support the conclusion that mouse brain exhibits functional heterogeneity of muscarinic receptors.