DIFFERENTIAL REGULATION BY BETA-AMYLOID PEPTIDES OF INTRACELLULAR FREE CA2+ CONCENTRATION IN CULTURED RAT MICROGLIA

We have previously shown that exposure to beta-amyloid peptides alters microglial activity and viability. It is thought that beta-amyloid pe ptides induce toxicity in neuronal cultures by destabilizing Ca2+ home ostasis. To investigate the effects of beta-amyloid peptides on intrac ellular free Ca2+ concentration ([Ca-?(2+)](i)) in cultured microglia, we used Fura-2 imaging. Exposure to 25 mu M beta-amyloid-(25-35) indu ced increases in [Ca-?(2+)](i) within 1 h. In contrast, exposure to 25 mu M beta-amyloid-(1-42), the full-length homolog to the beta-amyloid protein deposited in plaques, does not, over the same time period. Ho wever, the average [Ca2+](i) of microglia is increased by a 6 h exposu re to beta-amyloid-(1-42). Thus, beta-amyloid-(25-35) can alter [Ca-2](i) in microglia on a different time scale than beta-amyloid-(1-42), indicating a specificity in the response of these cells as compared to neurons.