Figure 2.

Mechanism of nAChR activation. (A) Acetylcholine (ACh) is synthesized, stored and released by cholinergic neurons. ACh is released from presynaptic neurons and binds to the nAChR of postsynaptic neurons to modulate the flow of ions across the cell membrane. (B) Three distinct functional states of the receptor exist: the closed, open and desensitized states; however, only the open state permits ion flux. (C) Chemical structures of the endogenous neurotransmitters ACh and serotonin (agonists).