EXCITATORY AMINO-ACID RECEPTORS INVOLVED IN PRIMARY AFFERENT-EVOKED POLYSYNAPTIC EPSPS OF SUBSTANTIA-GELATINOSA NEURONS IN THE ADULT-RAT SPINAL-CORD SLICE

Intracellular recordings were made from substantia gelatinosa (SG) neurons in spinal cord slices to determine a subclass of excitatory amino acid receptors involved in polysynaptic excitatory postsynaptic potentials (EPSPs). In the majority of neurons, polysynaptic EPSPs evoked by A-delta-fiber were not affected by 2-amino-5-phosphonovaleric acid (APV), while all EPSPs including monosynaptic EPSPs were depressed by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). All spontaneous EPSPs were blocked by CNQX, while spontaneous EPSPs in a few SG neurons were attenuated by APV. These observations suggest that polysynaptic EPSPs evoked through A-delta-fibers are predominantly mediated by activation of the non-N-methyl-D- aspartate (non-NMDA) receptor subclass.