(a) Mechanisms of action for direct cholinergic agonists. Direct cholinergic agonists can act by two ...

(a) Mechanisms of action for direct cholinergic agonists. Direct cholinergic agonists can act by two mechanisms: (1) drug causes more acetylcholine (Ach) to be released into the synaptic cleft, resulting in additional Ach to occupy Ach receptors; (2) drug binds to Ach receptors, enhancing the action potential on the postsynaptic neuron. (3) drug is inactivated by acetylcholinesterase (AchE). (b) Mechanism of action for indirect cholinergic agonists: (1) drug binds the enzyme (AchE), which prevents the Ach from being destroyed. This increases the amount of Ach remaining in the synaptic cleft, (2) thus enhancing the action potential on the postsynaptic neuron.