Edinburgh Napier University

  Rapid chemical communication between cells in the vertebrate central nervous system is mediated by ligand-gated ion-channel receptors (also called ionotropic receptors), which are multisubunit complexes, that each contain an ion-selective channel. In response to an appropriate signal, neurotransmitter is released from the storage vesicles in the presynaptic terminal of a neuron into the synaptic cleft; the signaling molecules then diffuse across this intercellular compartment and bind to receptors located in the membrane of the postsynaptic cell. The binding of neurotransmitter to an ionotropic receptor results, via an unknown mechanism that is assumed to involve a conformational change in the protein, in the opening of the ion channel and the flux of either cations or anions. This rapid neurotransmission, which occurs on the millisecond time scale, is terminated by the closure of the channel as a result of either agonist dissociation, or receptor desensitization, and either transmitter reuptake or hydrolysis.