The venom of the Indian red scorpion (Mesobuthus tamulus) triggers its autonomic storm through which molecular mechanism?
- A Binding to site 3 of voltage-gated sodium channels and delaying their inactivation ✓
- B Blockade of voltage-gated potassium channels, prolonging repolarisation of nerve terminals
- C Irreversible inhibition of acetylcholinesterase at autonomic ganglia
- D Direct agonist action on adrenal medullary nicotinic receptors
Correct answer: A. Binding to site 3 of voltage-gated sodium channels and delaying their inactivation
Explanation
Mesobuthus tamulus venom is an alpha-type scorpion toxin: it binds to receptor site 3 on voltage-gated sodium channels and slows their inactivation, causing persistent depolarisation and repetitive firing of autonomic nerves. This produces massive parasympathetic activation initially followed by a catecholamine surge from adrenals and sympathetic terminals, giving hypertension, arrhythmias and pulmonary oedema. Acetylcholinesterase inhibition is the organophosphate mechanism, and potassium channel blockade describes beta-type toxins of other genera.
Reference: Parikh's Textbook of Medical Jurisprudence and Toxicology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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