α-Bungarotoxin Blocks Excitatory Synaptic Transmission between Cercal Sensory Neurones and Giant Interneurone 2 of the Cockroach, Peripianeta Americana

Abstract

1. Autoradiographic localization of an 125I-α-bungarotoxin binding component revealed that specific binding was distributed mainly in the neuropile and to some extent in the periphery of the terminal abdominal ganglion of the cockroach, Periplaneta americana (L.). 2. Action potentials recorded from the axon of GI2 under current-clamp conditions were not affected by exposure to 1.0×10−5M α-bungarotoxin. 3. Excitatory postsynaptic potentials recorded from GI2, evoked by stimulation of cereal sensory neurones, were sensitive to block by relatively low concentrations (1.0×10−9-1.0×10−7 M) of α-bungarotoxin. The time-course for blockade was found to depend on toxin concentration and frequency of afferent stimulation. 4. Excitatory postsynaptic potentials recorded from GI 2 were not affected by exposure to 1.0×10−6M quinuclidinyl benzilate. 5. We conclude that at least a portion of the 125I-α-bungarotoxin binding component represents cholinergic receptors which have a postsynaptic function at synapses between cereal sensory neurones and GI 2.