Chapter 17 - Glutamate and Glutamate Receptors

Abstract

Publisher Summary Glutamate mediates most of the fast excitatory neurotrans­mission in the central nervous system, and it excites every neuron. Glutamate is the principal mediator of sensory information, motor coordination, emotions and cognition, including mem­ory formation and memory retrieval. The concentration of glu­tamate in brain gray matter structures varies between 10 and 15 μmol per gram of tissue, higher than in all other tis­sues of the body. In white matter the glutamate concentration is 4–6 μmol/g. Glutamate takes part in many reactions in the brain. The amino group of glutamate derives from serum amino acids that cross the blood–brain barrier. One defining characteristic of transmitter glutamate is its accumulation in synaptic vesicles. Specialized proteins in the vesicular membrane, the vesicu­lar glutamate transporters (VGLUTs) cause the accumulation of glutamate in synaptic vesicles. The fraction of glutamate contained in vesicles in gray mat­ter may be estimated from the density of glutamatergic synapses, the number of vesicles per terminal (100–500), the volume of each vesicle and the concentration of glutamate in the vesicles (60–250 mmol/l). Much of the glutamate that is released from the nerve terminals is taken up from the extracellular fluid into astrocytic processes that surround synapses.