Proteolytic enzymes do not destroy the N-methyl-D-aspartate (NMDA) sensitivity of acutely isolated hippocampal CA1 and CA3 neurons from postnatal rats.

Using whole cell recordings in combination with the concentration clamp technique it was shown that even enzymatically isolated hippocampal CA1 and CA3 neurons exhibit N-methyl-D-aspartate (NMDA) and L-aspartate currents. These currents were completely blocked by 0.5 mM Mg2+ or partially blocked (72.7 +/- 2.4%) by DL-2-amino-5-phosphonovalerate (50 microM) whereas 10 microM glycine (Gly) potentiated the NMDA responses (3.1 +/- 1.6-fold). A half-maximum dose of 55 microM was calculated from the sigmoid NMDA dose-response curve in the presence of 10 microM Gly. The amplitudes of these currents did not depend on the type of the proteolytic enzyme used for cell isolation.