Overview

Neurotransmitters evoke postsynaptic electrical responses by binding to members of a diverse group of proteins called neurotransmitter receptors. The receptors then give rise to electrical signals by opening or closing ion channels in the postsynaptic membrane. Whether the postsynaptic actions of a particular neurotransmitter are excitatory or inhibitory is determined by the class of ion channel affected by the transmitter, and by the concentration of permeant ions inside and outside the cell. There are two major classes of receptors: those in which the receptor molecule is also an ion channel, and those in which the receptor and ion channel are separate molecules. The former are called ionotropic receptors or ligand-gated ion channels, and give rise to fast postsynaptic responses that typically last only a few milliseconds. The latter are called metabotropic receptors, and they produce slower postsynaptic effects that may endure much longer. Numerous drugs affect the central nervous system by activating or blocking neurotransmission.