Neostigmine used in treatment of myasthenia gravis acts by:
**Core Concept**
Neostigmine is a cholinesterase inhibitor used in the treatment of myasthenia gravis, a chronic autoimmune disorder characterized by muscle weakness and fatigue. The underlying principle is that neostigmine increases the concentration of acetylcholine in the synaptic cleft by preventing its breakdown.
**Why the Correct Answer is Right**
Neostigmine acts by competitively inhibiting the enzyme acetylcholinesterase, which is responsible for breaking down acetylcholine. By inhibiting acetylcholinesterase, neostigmine allows more acetylcholine to accumulate in the synaptic cleft and bind to nicotinic receptors on the muscle endplate, thereby improving neuromuscular transmission and muscle strength. This mechanism is crucial for the treatment of myasthenia gravis, where there is a deficiency of acetylcholine receptors or an autoimmune blockage of these receptors.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the mechanism of action of neostigmine in myasthenia gravis.
**Option B:** This option is incorrect as neostigmine does not directly stimulate nicotinic receptors, but rather increases the availability of acetylcholine to bind to these receptors.
**Option C:** This option is not correct as neostigmine is not a direct agonist of nicotinic receptors, but rather a cholinesterase inhibitor.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that neostigmine is not a cure for myasthenia gravis but rather a symptomatic treatment that alleviates muscle weakness by improving neuromuscular transmission.
**Correct Answer: C. Inhibition of acetylcholinesterase.**