Shared antigenic determinant between the Electrophorus acetylcholine receptor and a synaptic component on chicken ciliary ganglion neurons.

Monoclonal antibodies raised against purified acetylcholine receptor from muscle and electric organ were tested for cross-reaction with surface components on chicken ciliary ganglion neurons. Indirect immunofluorescence indicated that antibodies to a determinant in the "main immunogenic region" of the receptor bind to the neurons in culture. Ultrastructural studies on 16-day embryonic ganglia, using horseradish peroxidase-conjugated monoclonal antibody, revealed that most of the conjugate labeling was associated with synaptic membrane on the neurons. A lesser amount of labeling was associated with the short processes extending from the neuronal somata in the region of preganglionic innervation. The labeling was blocked by coincubation with unlabeled antibodies of appropriate specificity and not by nonimmune serum. The pattern of labeling was clearly different from that previously found for a horseradish peroxidase conjugate of alpha-bungarotoxin: the toxin conjugate bound extensively to the short processes but not to synaptic membrane on the neurons. The synaptic antigen identified here by the cross-reacting antibodies is a candidate for the synaptic acetylcholine receptor on chicken ciliary ganglion neurons.