N-METHYL-D-ASPARTATE DEPRESSES GABA(A) RECEPTOR-MEDIATED CURRENTS IN NEURONS OF BULLFROG DORSAL-ROOT GANGLIA

The effect of N-methyl-D-aspartate (NMDA) on the function of GABAA rec eptors was examined in acutely dissociated neurons of bullfrog dorsal root ganglia (DRG) by using whole-cell patch clamp methods. The applic ation of NMDA (100 mu M) to DRG neurons suppressed the inward currents produced by GABA (100 mu M) and muscimol (100 mu M). DL-2-Amino-5-pho sphonovaleric acid (APV; 100 mu M) antagonized the NMDA-induced depres sion of the GABA current in a competitive manner. Kainic acid (100 mu M) did not depress the GABA current. NMDA induced no depression of the GABA current in a nominally Ca2+-free solution containing 5 mM Mg2+. These data indicate that the activation of the NMDA receptor inhibits the GABA(A) receptor-mediated current via a Ca2+-dependent process.