Nonequivalence of α bungarotoxin receptors and acetylcholine receptors in chick sympathetic neurons

S. T. Carbonetto, D. M. Fambrough, K. J. Muller

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α-Bungarotoxin binds selectively to chick sympathetic neurons that are responsive to iontophoretically applied acetylcholine. α-Bungarotoxin (125 nM) nM) does not affect the response of cultured neurons to acetylcholine, nor does it affect a cholinergic synaptic potential recorded from sympathetic ganglia. d-Tubocurarine (100-μM) inhibits α-bungarotoxin binding and blocks acetylcholine receptor function in both preparations, but α-bungarotoxin does not protect acetylcholine receptors against d-tubocurarine blockade of acetylcholine responses. The receptor for α-bungarotoxin can be extracted from neuronal membranes with nonionic detergents and, when assayed by velocity sedimentation in sucrose gradients, sediments at a rate faster than that of skeletal muscle acetylcholine receptors. Treatment of α-bungarotoxin-receptor complexes with glutaraldehyde (0.1%, wt/vol) increases their stability from a half time for dissociation of 3.5 hr to greater than 6 days at 23°. This permits a quantitative assay of α-bungarotoxin-receptor complexes after relatively long periods of velocity sedimentation. It is concluded that α-bungarotoxin does not bind to the acetylcholine-binding site of neuronal acetylcholine receptors. These results compel reevaluation of studies that assume that α-bungarotoxin is a specific ligand for neuronal acetylcholine receptors.

Original languageEnglish (US)
Pages (from-to)1016-1020
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number2
StatePublished - 1978
Externally publishedYes

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