Differentiation of kainate and quisqualate receptors in the cat spinal cord by selective antagonism with gamma-D(and L)-glutamylglycine.

The D and L forms of the dipeptide, gamma-glutamylglycine depress NMDA-, L-aspartate- and kainate-induced excitation in cat spinal cord while little or nor effect on L-glutamate- and quisqualate-induced responses. The dipeptides also depress dorsal root-evoked excitation of Renshaw cells, but not acetylcholine- or ventral root-evoked excitation of these cells. The D form of the dipeptide is more potent than the L form. The results are interpreted in favour of three types of receptors for excitatory amino acids on spinal neurones, these being sensitive to the selective agonist action of NMDA, kainate and quisqualate.