THE RELEASE OF AMINO-ACIDS FROM RAT NEOSTRIATUM AND SUBSTANTIA-NIGRA IN-VIVO - A DUAL MICRODIALYSIS PROBE ANALYSIS

It has previously been demonstrated. in dual probe microdialysis studi es, that stimulation of the neostriatum with kainic acid causes the re lease of GABA both locally within the neostriatum and distally in the substantia nigra, observations that are consistent with the known anat omy of the basal ganglia. The object of the present study was to furth er examine the characteristics of GABA release and to determine whethe r taurine, which has been proposed to be present in striatonigral neur ons, has similar characteristics of release, and to examine the releas e of excitatory amino acids under the same conditions. To this end, du al probe microdialysis studies were carried out on freely-moving rats. The application of kainic acid to neostriatum enhanced the release of GABA, taurine, aspartate and glutamate locally in the neostriatum and distally in the substantia nigra. The distal release of each amino ac id in the substantia nigra was sensitive to the administration of 6,7- dinitroquinoxaline-2,3-dione and tetrodotoxin to the neostriatum. Simi larly the local release of GABA, aspartate and glutamate but not tauri ne was sensitive to the intrastriatal application of 6,7-dinitroquinox aline-2,3-dione or tetrodotoxin. It is concluded that the release of t aurine from the substantia nigra has similar characteristics to that o f GABA and may be released from the terminals of striatonigral neurons following the stimulation of their cell bodies in the neostriatum. Th e release of taurine in the neostriatum however, is likely to be media ted mainly by different mechanisms and not related to neuronal activit y. The release of excitatory amino acids is likely to involve indirect effects in the neostriatum and polysynaptic pathways in the substanti a nigra. (C) 1998 IBRO. Published by Elsevier Science Ltd.