Relationship of acceptors for botulinum neurotoxins (types A and B) in rat CNS with the cholinergic marker, chol-I.

Localization in rat CNS of the acceptors for botulinum neurotoxin (types A and B) was examined by lesioning of cholinergic input to the cortex and immuno-affinity purification of cholinergic nerve terminals. Ibotenic acid lesions of the cortical cholinergic tract caused a small reduction in the content of high affinity binding sites for type A neurotoxin and a concomitant decrease in the activities of acetylcholinesterase and choline acetyltransferase. No such change was observed in the level of acceptors for BoNT B or the extent of immuno-labelling of Chol-I, a cholinergic ganglioside. Purification of cholinergic nerve terminals, using anti-(Chol-I) antibodies gave an equivalent enrichment in the acceptors (high and low affinity) for both toxin types and choline acetyltransferase. Neurotoxin type B (but not type A) inhibited binding of anti-(Chol-I) antibodies to this cholinergic ganglioside on nerve terminals and to semi-purified Chol-I. It can be deduced from these collective findings that the high affinity binding sites for BoNT A and possibly B are localized on cholinergic nerve terminals in the CNS and that the Chol-I ganglioside may be associated with the acceptor for type B toxin.