Blockade of N-methyl-D-aspartate response in enzyme-treated rat hippocampal neurons.

The responses to excitatory and inhibitory amino acids have been investigated in isolated pyramidal cells from young and adult rat hippocampus using internal perfusion and 'concentration-clamp' techniques. The neurons dissociated in a purely mechanical way were sensitive to all excitatory amino acids (glutamate, kainate, quisqualate and N-methyl-D-aspartate (NMDA] and inhibitory amino acids (glycine, taurine and gamma-aminobutyric acid). The NMDA response was dramatically potentiated by adding glycine at threshold concentration (10(-6) M). The enzyme treatment of hippocampal slices selectively removed the NMDA sensitivity but did not alter all other pharmacological properties of voltage- and agonist-gated ion channels.