The characterization of alpha-bungarotoxin receptors on the surface of parasympathetic neurons in the frog heart.

Receptors for alpha-bungarotoxin are found on the surface of parasympathetic neurons in the frog cardiac ganglion by light microscopic autoradiography. Competition studies suggest that these receptors are cholinergic and indicate that they are also recognized by neuronal bungarotoxin (kappa-bungarotoxin). These receptors are outnumbered by those recognized exclusively by neuronal bungarotoxin. Unlike neuronal bungarotoxin receptors, alpha-bungarotoxin receptors are not concentrated at synaptic sites. Fluorescence techniques fail to find evidence for clusters of alpha-bungarotoxin receptors anywhere on the neuronal surface. The possible function of these receptors, which apparently do not play a role in fast synaptic transmission, is discussed.