What mechanism primarily terminates the action of ACh in the synaptic cleft?

Acetylcholine (ACh) exerts its effects by binding to receptors in the synaptic cleft, but the termination of its action is crucial to ensuring that these signals are transient and tightly regulated. The primary mechanism for terminating ACh activity in the synaptic cleft is hydrolysis by acetylcholinesterase (AChE).

AChE is an enzyme that catalyzes the breakdown of ACh into acetate and choline. This rapid degradation is essential because it prevents prolonged stimulation of the postsynaptic receptors, allowing for normal synaptic function and signaling. The quick action of AChE ensures that once ACh has performed its signaling role, it is efficiently inactivated, allowing for the synaptic cleft to reset for subsequent nerve impulses.

In contrast, while uptake into neurons, diffusion, and binding to presynaptic receptors contribute to the dynamics of synaptic transmission, they do not represent the primary mechanism for inactivating ACh. Uptake may attempt to reclaim some ACh for recycling but is not the main method of termination. Similarly, diffusion helps disperse ACh away from the receptors, and binding to presynaptic receptors may modulate release but does not directly terminate its action in the cle