A patient complains of muscle weakness. It was reversed on the administration of neostigmine, because:

Neostigmine acts by inhibiting the enzyme acetylcholinesterase. This enzyme is involved in degradation of ACh, conse­quently neostigmine increases the synaptic level of ACh. Muscle weakness can be improved by stimulation of NM recep­tors at muscle end plate due to increased ACh.