CONTRIBUTIONS OF AMPA AND GABA(A) RECEPTORS TO THE INDUCTION OF NMDAR-DEPENDENT LTP IN CA1

The contributions of lpha-amino-3-hydroxy-5-methylisoxazole-4-propioni c acid (AMPA) and gamma-aminobutyric acid (GABA(A)) receptors in the i nduction of long-term potentiation (LTP) have been studied in the CA1 region of the rat hippocampus. The results suggest that: (1) in physio logical conditions, AMPARs are necessary for the induction of N-methyl -D-aspartate receptor (NMDAR)-dependent LTP since LTP cannot be elicit ed in the presence of the AMPAR antagonist, 6-cyano-7-nitroquinoxaline -2,3-dione (CNQX). Although a NMDAR-dependent LTP occurs in the presen ce of a GABA(A) antagonist and high concentrations of divalents cation s, blockade of AMPARs leads to a voltage-dependent calcium channels (V DCC)-dependent LTP since its induction is blocked by nifedipine and no t by APV. (2) The bicarbonate-induced GABA(A) receptor-mediated depola rizing response is not necessary in the induction of NMDAR-dependent o r VDCC-dependent LTP since induction of these two types of LTP were no t blocked by acetazolamide or in a nominally bicarbonate-free solution . (C) 1997 Elsevier Science Ireland Ltd.