Elapid venoms contain several neurotoxic components that block neuromuscular transmission at different sites. Which of the following produces paralysis by a PRESYNAPTIC mechanism?
- A Alpha-bungarotoxin
- B Cobrotoxin
- C Beta-bungarotoxin ✓
- D Erabutoxin b
Correct answer: C. Beta-bungarotoxin
Explanation
Beta-bungarotoxin, found in krait (Bungarus) venom, is a phospholipase A2 neurotoxin that acts presynaptically on the motor nerve terminal, initially causing repetitive transmitter release and subsequently blocking acetylcholine release altogether, producing irreversible paralysis. Alpha-bungarotoxin, cobrotoxin and erabutoxin are all three-finger toxins that bind postsynaptically to the nicotinic receptor at the motor end plate, competing with acetylcholine in a curare-like manner.
Reference: Parikh's Textbook of Medical Jurisprudence and Toxicology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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