Studies on the Nicotinic Cholinergic Receptor of Sympathetic Neurones

Abstract

In preparations of mammalian neurones, the few specific responses to acetylcholine mediated by a nicotinic receptor that have been recorded were found to be insensitive to α-bungarotoxin (α-BGT) (1–4). Various regions of the mammalian brain and ganglia, however, contain high affinity sites for α-bungarotoxin for which a physiological role has not yet been determined (for a review see (5)). These brain α-BGT binding proteins have been purified from rat (16) and mouse (17) brain and were found to be closely related, although not identical, to the neuromuscular junction acetylcholine receptors. The membrane located entities responsible for the α-BGT-insensitive nicotinic response have not been characterized so far and the possibility that they are distinct from the α-BGT binding proteins has received experimental supports (8, 17). Cultured neuronal cell lines of sympathetic origin are a particularly well-suited material for the resolution of this problem since they possess binding sites for α-bungarotoxin, as brain membrane preparations do, and have nicotinic receptors that can be functionally measured (6, 7) but are insensitive to α-bungarotoxin (2, 8, 9, 10).