NMDA-INDUCED INCREASE IN [CA2+]I AND CA-45(2+) UPTAKE IN ACUTELY DISSOCIATED BRAIN-CELLS DERIVED FROM ADULT-RATS

A preparation of acutely dissociated brain cells derived from adult (3-month-old) rat has been developed under conditions preserving the metabolic integrity of the cells and the function of N-methyl-D-aspartate (NMDA) receptors. The effects of glutamate and NMDA on [Ca2+]i measured with fluo3 and Ca-45(2+) uptake have been studied on preparations derived from hippocampus and cerebral cortex. Glutamate (100-mu-M) and N-methyl-DL-aspartate (200-mu-M) increased [Ca2+]i by 26-12 nM and 23-9 nM after 90 s in cerebral cortex and hippocampus, and stimulated Ca-45(2+) uptake about 16-10% in the same regions. The increases in [Ca2+]i and Ca-45(2+) uptake were inhibited by 40% in the presence of 1 mM MgCl2 and by 90-50% in the presence of MK-801. The results indicate (a) that a large fraction of the [Ca2+]i response to glutamate in freshly dissociated brain cells from the adult rat involves NMDA receptors, (b) when compared with results in newborn rats, there is a substantial blunting of the [Ca2+]i increase in adult age.