Exocytic release of ACH is blocked by -

Ans. is 'b' i.e., Botulinum [Ref: KDT 7th/ep. 99-100)ACETYLCHOLINE SYNTHESIS AND RELEASEo Choline is actively taken up by the axonal membrane by Na+; choline cotransporter. (Rate limiting step). This step is blocked by Hemicholinium.o Choline is acetylated with the help of ATP and coenzyme 'A' by the enzyme choline acetyl transferase present in the axoplasm.ATP + Acetate +- Co-A - Acetyl Co-ACholine------------Choline-acetyl transferaseAcetylcholine + CoAo Synthesized ACH is actively transported into synaptic vesicle. This step is inhibited by vesamicolo ACH is released from nerve terminals by exocytosis of vesicles. This step is interfered by :Botulinum toxin - Inhibits releaseBlack widow spider toxin - Induces massive release and depletion,o Acetylcholine is inactivated by acetylcholinestrase.o Pralidoxime reactivates AChE.