Presynaptic effect of L-glutamic acid on the release of dopamine in rat striatal slices

The release of ³H] dopamine (³H] DA) was estimated in serial superfusate fractions of rat striatal slices continuously superfused with L-3,5-³H]-tyrosine. L-glutamic acid (5 · 10^?5 M), but not the D-stereoisomer, increased the spontaneous release of ³H] DA (60%). The stimulating effect of L-glutamic acid was still observed in the presence of tetrodotoxin (5 · 10^?7 M), suggesting that the amino-acid acts at a presynaptic site. Moreover, atropine (10^?6 M) or pempidine (10^?5 M) which blocks the acetylcholine (ACh) evoked release of ³H] DA did not reduce the stimulatory effect of L-glutamic acid on ³H] DA release, thus excluding the possible intervention of striatal cholinergic neurons. The data obtained support the hypothesis of a direct control of DA release from nerve terminals by glutamatergic neurons.