Extracellular levels of amino acids in striatum and globus pallidus of 6-hydroxydopamine-lesioned rats measured with microdialysis.

Extracellular aspartate, glutamate, glutamine, taurine and GABA concentrations were measured by microdialysis in the rat striatum and globus pallidus after a unilateral 6-hydroxydopamine lesion of the dopamine system. The basal and potassium-evoked overflow of GABA was increased in the ipsilateral striatum, but the evoked overflow was decreased in both contralateral striatum and pallidum. Both basal and evoked overflow of glutamate was increased in ipsilateral striatum. The basal overflow of aspartate was significantly increased in the ipsilateral side. Basal glutamine on the other hand was decreased in the ipsilateral side. Taurine remained unchanged in both regions. These results suggest that dopamine is involved in the regulation of transmission by GABA and glutamate. Since glutamine might be the precursor to glutamate, the change in glutamate might affect the glutamine level. The changed aspartate level has no obvious explanation.