A polyclonal, monospecific antiserum raised against a nicotinic acetylcholine receptor protein affinity-purified from insect nervous tissue, was employed to demonstrate the localization of antigenic sites in the neuropile of the terminal (sixth) abdominal ganglion of the cockroach
Periplaneta americana
. In agreement with previously published autoradiographic mapping of specific [
125
I]
α
-bungarotoxin binding sites, specific areas of the central neuropile of this ganglion were densely stained, but not the cereal afferent axons. No staining was detected corresponding to the dense, peripheral, partly non-specific binding of
α
-bungarotoxin seen in autoradiographs of the same tissue. Certain peripherally located neuronal cell bodies, including the cell body of giant interneuron 2, contained intracellularly located antigenic sites.
