Ethanol inhibition of N-methyl-D-aspartate-activated current in mouse hippocampal neurones: whole-cell patch-clamp analysis

1 The action of ethanol on N-methyl-D-aspartate (NMDA)-activated ion current was studied in mouse hippocampal neurones in culture using whole-cell patch-clamp recording. 2 Ethanol inhibited NMDA-activated current in a voltage-independent manner, and did not alter the reversal potential of NMDA-activated current. 3 Concentration-response analysis of NMDA-and glycine-activated current revealed that ethanol decreased the maximal response to both agonists without affecting their EC50 values. 4 The polyamine spermine (1 mu M) increased amplitude of NMDA-activated current but did not alter the percentage inhibition of ethanol. 5 Compared to an extracellular pH of 7.0, pH 6.0 decreased and pH 8.0 increased the amplitude of NMDA-activated current, but these changes in pH did not significantly alter the percentage inhibition by ethanol. 6 The sulphydryl reducing agent dithiothreitol (2 mM) increased the amplitude of NMDA-activated current, but did not affect the percentage inhibition by ethanol. 7 Mg2+ (10, 100, 500 mu M), Zn2+ (5, 20 mu M) or ketamine (2, 10 mu M) decreased the amplitude of NMDA-activated current, but did not affect the percentage inhibition by ethanol. 8 The observations are consistent with ethanol inhibiting the function of NMDA receptors by a noncompetitive mechanism that does not involve several modulatory sites on the NMDA receptor-ionophore complex.