Stereospecific 3H-QNB binding to human erythrocyte membranes associated with muscarinic cholinergic receptors.

Specific binding of the muscarinic antagonist 3H-QNB can be demonstrated on human erythrocyte membranes. Specific 3H-QNB binding is stereospecific and can be inhibited by a variety of cholinergic agonists and antagonist with affinities similar to their affinities for muscarinic cholinergic receptor binding in other tissues. Accordingly, the data indicate the presence of muscarinic cholinergic receptors on human erythrocyte membranes. Their density is very low, varies between healthy persons, but seems to be an individual characteristic. The data reported are consistent with the assumption that the muscarinic cholinergic receptors on human erythrocyte membranes are mainly of the M1 receptor subtype.