How do pyrethroids and neonicotinoids differ in their mechanism of action?

How do pyrethroids and neonicotinoids differ in their mechanism of action?

• A. Pyrethroids disrupt voltage-gated sodium channels; neonicotinoids bind and overstimulate nicotinic acetylcholine receptors.
• B. Pyrethroids inhibit acetylcholinesterase; neonicotinoids block GABA receptors.
• C. Pyrethroids and neonicotinoids both disrupt voltage-gated sodium channels.
• D. Pyrethroids bind to nicotinic receptors; neonicotinoids disrupt chloride channels.

Answer: (A)

The main concept is that insecticides can kill by targeting different parts of the nervous system. Pyrethroids keep voltage-gated sodium channels open for longer than normal, which causes neurons to fire repeatedly, leading to hyperactivity and paralysis. Neonicotinoids, in contrast, act on postsynaptic nicotinic acetylcholine receptors, binding as agonists and overstimulating neurons, which also results in paralysis and death. This option is the best because it accurately describes those distinct mechanisms: pyrethroids disrupt sodium channel function, while neonicotinoids directly stimulate nicotinic acetylcholine receptors. Mechanisms like inhibiting acetylcholinesterase or blocking GABA receptors belong to other pesticide classes, and pyrethroids do not act on nicotinic receptors or chloride channels in the way described by the other choices.

The main concept is that insecticides can kill by targeting different parts of the nervous system. Pyrethroids keep voltage-gated sodium channels open for longer than normal, which causes neurons to fire repeatedly, leading to hyperactivity and paralysis. Neonicotinoids, in contrast, act on postsynaptic nicotinic acetylcholine receptors, binding as agonists and overstimulating neurons, which also results in paralysis and death.

This option is the best because it accurately describes those distinct mechanisms: pyrethroids disrupt sodium channel function, while neonicotinoids directly stimulate nicotinic acetylcholine receptors. Mechanisms like inhibiting acetylcholinesterase or blocking GABA receptors belong to other pesticide classes, and pyrethroids do not act on nicotinic receptors or chloride channels in the way described by the other choices.