Which one of the following statement is correct as regards mode of action of synthetic pyrethroids:

Correct option is D

Synthetic pyrethroids are a class of neurotoxic insecticides modeled after natural pyrethrins found in chrysanthemum flowers. They are widely used in agricultural, veterinary, and household pest control due to their high insecticidal potency and low mammalian toxicity.
�� Mode of Action of Synthetic Pyrethroids:
· Pyrethroids act on the axon of nerve cells.
· They disrupt the normal functioning of voltage-gated sodium (Na⁺) channels in nerve membranes.
· Normally, these sodium channels open briefly to allow sodium ions into the neuron, initiating nerve impulses, and then close quickly.
· Pyrethroids cause these sodium channels to remain open for extended periods, resulting in prolonged depolarization.
· This leads to repetitive nerve firing, loss of coordination, paralysis, and eventually death of the insect.
Thus, option (d) accurately describes the true physiological mechanism of pyrethroids.
❌ Explanation of Incorrect Options:
(a) Inhibition of synaptic transmission by inhibiting the enzyme acetylcholine esterase:
· This is the mode of action of organophosphates and carbamate insecticides, not pyrethroids.
· These compounds prevent the breakdown of acetylcholine, causing excessive nerve stimulation.
(b) Stomach toxicant:
· Pyrethroids are primarily contact and inhalation poisons, not stomach poisons.
· They affect insects through cutaneous absorption and respiratory exposure, rather than ingestion.
(c) Inhibition of electron transport in mitochondria:
· This describes the mode of action of fumigants like fluoroacetate or certain insecticidal oils, not synthetic pyrethroids.