Effect of Pyrethrum on mosquitoes is described as –
**Core Concept**
Pyrethrum is a natural insecticide extracted from the flowers of the daisy-like plant Chrysanthemum cinerariifolium. It acts on the nervous system of insects, primarily mosquitoes, by altering the function of their ion channels and receptors.
**Why the Correct Answer is Right**
Pyrethrum's mode of action involves the activation of sodium channels in the insect nervous system, leading to an influx of sodium ions and depolarization of the neuron. This results in repetitive firing of neurons, causing muscle contractions and ultimately leading to the death of the mosquito. Pyrethrum also affects the insect's GABA-gated chloride channels, further contributing to its neurotoxic effects.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pyrethrum does not primarily act through the inhibition of acetylcholinesterase, an enzyme involved in the breakdown of acetylcholine.
**Option B:** This option is incorrect because pyrethrum does not primarily act through the inhibition of monoamine oxidase, an enzyme involved in the breakdown of monoamines.
**Option C:** This option is incorrect because pyrethrum does not primarily act through the inhibition of cytochrome P450 enzymes, which are involved in the metabolism of various substances.
**Clinical Pearl / High-Yield Fact**
Pyrethrum is a natural insecticide that has been used for centuries in traditional medicine and as a pest control agent. Its mode of action provides a useful example of how altering ion channel function can lead to neurotoxicity in insects.
**Correct Answer:** D.