COMPARISON OF TRANSMITTER AMINO-ACID LEVELS IN RAT GLOBUS PALLIDUS AND NEOSTRIATUM DURING HYPOGLYCEMIA OR AFTER TREATMENT WITH METHIONINE SULFOXIMINE OR GAMMA-VINYL GAMMA-AMINOBUTYRIC-ACID

The levels of amino acids in globus pallidus, a structure heavily innervated with γ‐aminobutyric acid (GABA)‐ergic terminals but few glutamergic terminals, were compared with the levels in neostriatum, a structure richly innervated with glutamergic terminals but intermediate in GABAergic terminals. The level of glutamate in neostriatum was twice as high as in globus pallidus whereas the level of GABA in globus pallidus was three times higher than in neostriatum. The level of aspartate was similar in both regions whereas the level of glutamine was correlated with the level of glutamate. Methionine sulfoximine, a glutamine synthetase inhibitor, reduced the level of glutamine to 10‐20% of control in both structures. This reduction was accompanied by the largest decrease in the level of glutamate in neostriatum, indicating that transmitter glutamate turns over more rapidly than other glutamate pools. Likewise, insulin decreased the levels of glutamate and glutamine more in neostriatum than in globus pallidus. γ‐Vinyl GABA increased the level of GABA in globus pallidus more than in neostriatum although the percent increase was largest in neostriatum. Treatment with γ‐vinyl GABA was accompanied by a large reduction in the level of glutamine that was correlated with the increase in the level of GABA, indicating that a substantial proportion of the glutamine pool is linked to GABA metabolism. Copyright © 1990, Wiley Blackwell. All rights reserved