In organophosphorus compound poisoning, organophosphorus compound actions are –
**Core Concept**
Organophosphorus compound poisoning occurs due to the inhibition of acetylcholinesterase, an enzyme responsible for breaking down the neurotransmitter acetylcholine. This leads to an accumulation of acetylcholine in the synaptic cleft, causing overstimulation of cholinergic receptors.
**Why the Correct Answer is Right**
Organophosphorus compounds, such as those found in pesticides and nerve agents, irreversibly inhibit acetylcholinesterase by forming a covalent bond with the enzyme. This results in a buildup of acetylcholine, leading to overstimulation of muscarinic and nicotinic receptors. The muscarinic receptors are responsible for the parasympathetic effects, such as bradycardia, bronchospasm, and miosis, while the nicotinic receptors are responsible for the neuromuscular effects, such as muscle fasciculations and paralysis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because organophosphorus compounds do not primarily act through the inhibition of butyrylcholinesterase, a pseudocholinesterase that is involved in the hydrolysis of certain esters.
* **Option B:** This option is incorrect because organophosphorus compounds do not primarily act through the inhibition of acetylcholine receptors, which are the target of certain neuromuscular blocking agents.
* **Option C:** This option is incorrect because organophosphorus compounds do not primarily act through the inhibition of monoamine oxidase, an enzyme involved in the breakdown of certain neurotransmitters such as serotonin and dopamine.
**Clinical Pearl / High-Yield Fact**
Atropine is a muscarinic receptor antagonist that is often used as an antidote in organophosphorus compound poisoning, as it can help to counteract the parasympathetic effects such as bradycardia and bronchospasm.
**Correct Answer: C. Inhibition of acetylcholinesterase.**