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Increase in reactive cholesterol in the presynaptic membrane of depolarized Torpedo synaptosomes: blockade by
1Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Hospital de Bellvitge, Universitat de Barcelona, Barcelona, Spain.
Abstract:
We have investigated the redistribution of filipin-cholesterol complexes at freeze-fractured presynaptic membrane of pure cholinergic synaptosomes isolated from Torpedo electric organ during acetylcholine release. After chemical depolarization, filipin-induced lesions increase at the presynaptic membrane. These changes do not take place when synaptosomes are stimulated in a calcium-free medium. Botulinum neurotoxin type A blocks both acetylcholine release and the rearrangement of filipin-induced lesions induced by depolarization. Since botulinum neurotoxin type A does not block either membrane depolarization or calcium entry into the nerve terminal, our results suggest that the redistribution of filipin-cholesterol complexes is linked to the acetylcholine release process.