High-affinity hemicholinium-3 binding to brain membranes: reduction by treatment with physostigmine in vivo.

We examined high-affinity, sodium-dependent binding of hemicholinium-3 to brain membranes. Binding, with Kd of about 3 nM, was highest in corpus striatum, intermediate in cerebral cortex and hippocampus, and low in cerebellum. Treatment with physostigmine in vivo reduced binding in all regions without affecting apparent affinity.