EFFECTS OF GLUTAMATE, ASPARTATE, AND 2 PRESUMED ANTAGONISTS ON FELINE RUBROSPINAL NEURONS

The actions of dicarboxyl amino acids (GLUT [glutamate], ASP [aspartate], DLH [DL-homocysteate]) and of presumed amino acid antagonists (GDEE [glutamate diethylester], HA 966 [1-hydroxy-3-aminopyrrolidone-2]) were studied in rubrospinal neurons with microelectrophoretic techniques. ASP and GLUT reversibly depolarized the cell membrane and increased its conductance. ASP had slightly stronger actions than GLUT. DLH had strong depolarizing actions without a clearcut change in membrane conductance; this may be due to the fact that DLH effects did not involve synaptic receptors. A specific action as antagonists for GLUT could not be shown for GDEE or HA 966. HA 966 effects were often accompanied by apparent postsynaptic actions. GDEE antagonized DLH effects sometimes even stronger than GLUT effects. GLUT and ASP behaved as excitatory transmitters. The demonstration of a role as transmitter substances in excitatory (e.g., corticorubral or interpositorubral) pathways still awaits the specific pharmacological antagonist.