Involvement of K+ Channels in the Inhibitory Effects of Adenosine on Anoxia-Induced [Ca2+ ]i Increase in Cultured Rat Hippocampal CA1 Neurons

Changes in intracellular free Ca2+ concentration ([Ca2+]i) in cultured hippocampal CA1 neurons isolated from newborn rats were measured by a confocal laser scanning microscope, using the Ca2+ indicator Fluo-3. The results showed that exogenous adenosine (100 (mu)M) significantly attenuated the increase of neuronal [Ca2+]i induced by acute anoxia. This effect of adenosine could be suppressed by the adenosine A1 receptor antagonist 8-cyclopentyltheophylline. Moreover, potassium channel blockers, aminopyridine, and glipizide could also block the inhibitory role of adenosine, but tetraethylammonium had no effect. These results suggest that adenosine may activate 4-AP or ATP-sensitive potassium channels via an A1-receptor-mediated mechanism and consequently inhibit anoxia-induced [Ca2+]i elevation in hippocampal neurons.