NMDA receptors at excitatory synapses in the hippocampus: test of a theory of magnesium block

Abstract

Excitatory postsynaptic currents (EPSCs) were studied using the whole-cell patch-clamp technique to record from rat hippocampal pyramidal neurons in both slices and dissociated cultures. The voltage- and magnesium-dependence of the N-methyl-d-aspartate (NMDA) component of the EPSCs was quantified by measuring the amplitude of this component at a range of holding potentials (-80 mV to 60 or 80 mV) in several bath magnesium concentrations (0.2μM, 0.1, 1 and 10 mM). All of our results were well-fitted by a theory of magnesium block developed from single-channel studies of extrajunctional NMDA channels in culture. It is concluded that extrasynaptic and subsynaptic NMDA channels both in culture and in situ have identical properties of magnesium block. Show more