Muscarinic cholinergic receptors in a rat phaeochromocytoma cell line.

The high affinity binding of the muscarinic ligand 3H-N-methylscopolamine (3H-NMS) to intact cells of the rat pheochromocytoma cell line PC12 was studied. A single class of saturable binding sites was observed with a density of about 5000 sites per cell, and a pharmacological profile consistent with muscarinic receptors. The inhibition of 3H-NMS binding by the antagonist pirenzepine was of low affinity suggesting PC12 muscarinic receptors may be similar to those found on rat sympathetic nerve terminals.