In Myasthenia Gravis, autoantibodies are directed against which receptor?

• A. Dopamine receptor
• B. Acetylcholine receptor
• C. GABA receptor
• D. NMDA receptor

Answer: (B)

Myasthenia Gravis involves an autoimmune attack on the postsynaptic acetylcholine receptors at the neuromuscular junction. The antibodies bind these nicotinic receptors, prompting their removal from the motor endplate and often activating complement to damage the surface. With fewer functional receptors, acetylcholine’s signal is less effectively translated into a muscle action potential, so muscle strength wanes with repeated use and fatigue sets in quickly. This explains features like ptosis and diplopia that worsen with activity and improve with rest. Other receptors listed—dopamine, GABA, and NMDA—belong to the central nervous system and are not the targets of autoantibodies in this disease, so they do not explain the neuromuscular weakness seen in MG. (Note: a minority of MG patients have antibodies to MuSK, but the classic target is the acetylcholine receptor.)