Synaptic localization of alpha-bungarotoxin binding which blocks nicotinic transmission at frog sympathetic neurons.

摘要: Abstract Sympathetic neurons receive direct synaptic input from cholinergic terminal boutons of preganglionic nerve fibers. The distribution acetylcholine receptors at these synapses is not precisely known. This study shows that alpha-bungarotoxin, which binds specifically to nicotinic on skeletal muscle, also may be useful for localizing postsynaptic principal in the paravertebral sympathetic ganglia bullfrog. alpha-Bungarotoxin (1-5 microM) produces a block (fast) excitatory potentials fully reversed after 5-8 hr washing. Dihydro-beta-erythroidine, antagonist, reduces half-time recovery toxin one-third control value, presumably by competing same receptor sites. Furthermore, response applied carbachol reduced toxin, indicating transmission due decreased membrane. Peroxidase-labeled alpha-bungarotoxin localized small (0.2- 0.5-micrometers diameter) patches beneath boutons. Peroxidase reaction product restricted regions cleft just opposite active zones presynaptic terminal. In addition, peroxidase-labeled antibodies against Torpedo bind exclusively regions; evidently are areas concentrated contacts neurons.