RELATIONSHIP OF ALPHA-BUNGAROTOXIN BINDING-ACTIVITY AND CHOLINERGIC TERMINATION WITHIN THE RAT HIPPOCAMPUS

The disposition of receptors for α-bungarotoxin in the rat hippocampus during postnatal development and in response to septal lesions was studied using light-microscopic autoradiography. The temporal and spatial relationships of toxin receptors and presynaptic cholinergic elements, identified by acetylcholinesterase staining and amino acid tracer techniques, was analyzed in particular. It was found that (a) toxin binding sites arise very early, probably prior to the ingrowth of cholinergic fibers; (b) toxin receptors develop normally in the absence of a cholinergic termination brought about by septal lesion; and (c) two areas of marked toxin binding activity fall outside regions of identified cholinergic termination, one appearing transiently in early development, another persisting in the adult animal. It is concluded that, in the rat hippocampus, binding sites for α-bungarotoxin, which are likely to be related to nicotinic acetylcholine receptors, develop independently of cholinergic input and may to some extent subserve functions other than synaptic transmission. © 1979.