Abstract: Objective To investigate the acute effect of apolipoprotein E（apoE）on the intracellular free Ca2+ in rat cortical neurons. Methods The intracellular resting calcium level in cultured primary rat cortical neurons was measured by using confocal fluorescent imaging technique. MK-801, an N-methyl-D-aspartate (NMDA) receptor noncompetitive antagonist, was employed to test whether NMDA receptor was implicated in the effect of apoE4. Results Acute application of apoE4, but not apoE3, significantly increased the resting [Ca2+]i in a dose- and time-dependent manner (P<0.01 or P<0.05), and MK-801 partly blocked the apoE4-induced elevation of resting [Ca2+]i (P<0.05 or P<0.01). Conclusion ApoE4 acutely disturbs calcium homeostasis, and the activation of NMDA receptor may play a critical role in the intracellular calcium overload induced by apoE4 and its neurotoxicity.

Key words: ApolipoproteinE (apoE), Fluo-3/AM, Laser scanning confocal microscopy(LSCM), calcium