Postmortem Changes in Binding to the Muscarinic Receptor from Human Cerebral Cortex

Abstract
The effects of storage at 4°C on the antagonist and agonist binding properties of the muscarinic acetyl‐choline receptor from fresh surgical and frozen autopsy samples from human cerebral cortex were studied. The number of 1‐[3H]3‐quinuclidinyl benzilate binding sites and their affinities were stable up to 51 h, both when stored as pieces of intact nonfrozen tissue and as a homogenate. The agonist binding properties as measured by the ability of the muscarinic agonist carbachol to compete with l‐[3H]3‐quinuclidinyl benzilate were also stable up to 51 h when the tissue was stored in the form of pieces. The affinity for carbachol decreased when the tissue was stored as a homogenate. The frozen autopsy samples showed no significant differences in binding properties in comparison with fresh neurosurgical tissue.