Glutamate Pools in the Brain

Glutamate has a central role in brain metabolism, as well as being a transmitter and a precursor for GABA. It is therefore of interest to define and quantify the different glutamate pools. The size of these pools will differ from area to area and species to species (Fig. 3). 

The transmitter pool of glutamate may be quantified after selective degeneration of the glutamate terminals by surgical or chemical lesions. By this technique the transmitter glutamate pool has been found to be 20-30% of the total glutamate content in neostriatum, thalamus, lateral septum, nucleus accumbens, and 

The proportion of glutamate in the small glutamate pool, i.e., the glial cells, can be estimated from the relative specific radioactivity of glutamine compared to glutamate after administration of group 1 precursors (acetate, aspartate, NaHCOj). In several re- 

The remaining glutamate must be ascribed to other neuronal structures and coupled to the general metabolism in neurons. This IS by far the largest pool and probably accounts for about half of the glutamate content in the brain. In neostriatum, the neuronal cell bodies are destroyed by kamic acid injection. Such treatment is accompanied by 50% loss of glutamate in the neostriatum (Nicklas et al., 1979). 

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