Neuronal nicotinic alpha-bungarotoxin receptors.
Recent evidence has indicated that the nicotinic acetylcholine receptor and the nicotinic alpha-bungarotoxin (alpha-BGT) site may be distinct in neuronal tissues. With regard to function, the former receptor appears to be involved in mediating synaptic events; however, the role of the nicotinic alpha-BGT site in nervous tissue is currently not known. Since the binding of alpha-BGT exhibits such high affinity and selectivity for a specific receptor, this may implicate an involvement of the toxin binding site in some aspect of neuronal activity with the receptor possibly mediating functions other than nicotinic cholinergic transmission. A further hypothesis to explain the nature of the toxin binding site may be that the natural ligand for the alpha-BGT site is one other than acetylcholine, with acetylcholine acting as a modulator of the site. Current studies in our laboratory are exploring these possibilities by determining whether specific peptides and/or polypeptides can interact at the nicotinic alpha-BGT site in nervous tissue. Studies using both in vivo and in vitro approaches suggest that thymopoietin may serve a role as a modulator of the nicotinic alpha-BGT site in neuronal tissues.