Which class of pesticides inhibits acetylcholinesterase, leading to nerve dysfunction?

• A. Organophosphates
• B. Pyrethroids
• C. Neonicotinoids
• D. Carbamates

Answer: (A)

Inhibition of acetylcholinesterase prevents the breakdown of acetylcholine in the synaptic cleft, so acetylcholine keeps stimulating nerves rather than being cleared. This leads to overstimulation of cholinergic receptors, causing rapid, disorganized nerve signaling, muscle twitching, paralysis, and ultimately nerve dysfunction.

Organophosphates are the classic class that do this: they bind to acetylcholinesterase and form a stable, often irreversible complex, so the enzyme can no longer terminate acetylcholine signaling for a prolonged period. That sustained disruption is why these compounds are potent insecticides, though they pose significant risks to non-target animals as well.

Carbamates also inhibit acetylcholinesterase but in a reversible, shorter-acting way, so their effects wear off sooner. Pyrethroids act differently by keeping sodium channels open to cause repeated nerve firing, not by blocking acetylcholinesterase. Neonicotinoids target nicotinic acetylcholine receptors themselves, causing overstimulation through receptor activation rather than enzyme inhibition.