DEVELOPMENTAL-CHANGES IN THE VOLTAGE-DEPENDENCE OF NEOCORTICAL NMDA RESPONSES

A change in the response of neocortical neurons to N-methyl-D-aspartat e (NMDA) was observed during the first 2 weeks of postnatal developmen t. When NMDA was bath applied, the membrane current-voltage relationsh ip recorded in neurons from postnatal day (PN) 3-5 rats displayed a re gion of decreased inward current at hyperpolarized membrane potentials . By PN 9-14, the net inward current at hyperpolarized potentials was significantly less than that recorded in PN 3-5 neurons. These results indicate that a developmental increase in the voltage-dependence of N MDA responses exists, which may be due to changes in magnesium sensiti vity of the NMDA receptor.