NMDA and AMPA receptors mediate intracellular calcium increase in rat cortical astrocytes.

AIM To study the effect of glutamate on the intracellular calcium signal of pure cultured rat astrocytes and the role of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors in the procedure. METHODS The fluorescence of calcium was measured by Fura-2/AM (F(345)/F(380)). RESULTS L-Glutamate induced [Ca(2+)](i) increase in most of the cells in concentration- and time-dependent manner. NMDA 50 mmol/L induced the fluorescence increase by almost three to four times, while the effect of AMPA 50 mmol/L was just half of that of D-(-)-2-amino-5-phosphonopentanoic acid (D-AP-5; a selective antagonist of the NMDA receptor). 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX, a selective antagonist of the AMPA receptor) abolished the effects of NMDA and AMPA, respectively. D-AP-5 and CNQX simultaneously or respectively attenuated the effect of L-glutamate at different degrees, but could not abolish it entirely. CONCLUSION Glutamate modulated intracellular Ca(2+) of pure cultured rat astrocytes through different pathways. The activation of NMDA and AMPA receptors took part in the complex mechanisms.