α-Bungarotoxin binding sites in the CNS

The neurotoxin α-bungarotoxin (BuTX) has been extensively used as a specific and irreversible ligand to study the nicotinic acetylcholine receptor (nAChR) in skeletal muscle and electric fish. More recently it has been utilized to investigate the possibility of nAChRs in the CNS. The BuTX binding sites in the CNS have biochemical properties similar to muscle, have a distribution similar to other cholinergic markers, and have been histologically demonstrated to bind to post-synaptic membranes. But studies of ganglionic neurons, cultured sympathetic ganglion cells, and the PC 12 cell culture line have raised questions regarding the use of BuTX as a nicotinic receptor ligand in the CNS. The evidence for and against BuTX as a nicotinic receptor ligand is reviewed and discussed.