[Calcium channels associated with glutamate receptors]

Ionotropic glutamate receptors are nowadays classified into two major categories based on the sensitivity to N-methyl-D-aspartic acid(NMDA) in the mammalian central nervous system. The NMDA channel has much higher permeability to Ca2+ than the non-NMDA channels in most situations, while point mutation could lead to increased permeation of Ca2+ across the non-NMDA channels. Opening of the NMDA channel is under control by a variety of endogenous low molecules, including glycine, polyamines, Mg2+, Zn2+ and H+, in addition to modulation by Ca2+/calmodulin, protein kinases and protein phosphatases. Moreover, the NMDA channel contains a redox site modulatory for the opening. Recent molecular cloning studies have revealed that the NMDA channel is a protein complex consisting of different subunits such as NMDAR1 and NMDAR2 with heterologous expression in the brain. Studies on mice knocked out of a particular gene argue in favor of an essential role of the corresponding subunits in molecular mechanisms underlying neuronal network formation and synaptic plasticity.