EXCITABILITY OF NEURAL ELEMENTS WITHIN THE RAT CORPUS STRIATUM

The excitability of cholinergic, glutamatergic and dopaminergic elemen ts within the rat neostriatum was studied in both in vivo and in vitro preparations. In vivo, the microdialysis technique was used to measur e the release of striatal acetylcholine and dopamine under basal and e lectrically evoked conditions. For comparison, acetylcholine, dopamine and glutamate release was assayed in media obtained from superfused r at striatal slices. Electrical stimulation was used to derive the stre ngth-duration functions and their chronaxies of stimulated elements co ntaining the three neurotransmitter types. The chonaxies for experimen ts in vitro and in vivo were similar: the chronaxy values for elements containing acetylcholine were the shortest, the values for glutamate were intermediate, and the values for those containing dopamine were t he longest. Based on the chronaxy estimates, it is proposed that the e lements containing acetylcholine are the large cholinergic interneuron s of striatum, and the elements containing glutamate and dopamine are the terminals of corticostriatal and nigrostriatal neurons, respective ly. These results indicate that electrical stimulation of neural eleme nts surrounding a microdialysis probe can be an additional tool to exa mine the factors that regulate neurotransmitter release. Likewise, inv estigators can activate specific striatal elements by using pulse dura tions that coincide with their chronaxies. (C) 1997 Elsevier Science B .V.