[Neurochemistry of the mesencephalic substantia nigra: interrelations between excitatory amino acids, N-methyl-D-aspartate type receptors and intrinsic neuronal systems].

Recent studies have demonstrated the existence of cortico-nigral fibers in the brain which may use L-glutamic or L-aspartic acid as their transmitters. Such cortico-nigral neuronal pathway seems to functionally interact with intrinsic neuronal systems in substantia nigra (SN) by first activating different subtypes of excitatory amino acid (EAA) receptors. Particularly interesting are results showing that activation of N-methyl-D-aspartate (NMDA) subtype receptor may evoke the Ca(2+)-dependent release of dopamine from dendrites of nigro-striatal neurons. In addition, NMDA and other EAA receptors may influence the functional activity of gabaergic, glycinergic and peptidergic neurons located in SN. Acidic aminoacid-containing neurons in SN may thus play a pivotal role in determining the outflow information from SN to caudal motor-related as well as rostral limbic-related areas in the brain.