P2Y13 receptor-mediated rapid increase in intracellular calcium induced by ADP in cultured dorsal spinal cord microglia.

P2Y receptors have been implicated in the calcium mobilization by the response to neuroexcitatory substances in neurons and astrocytes, but little is known about P2Y receptors in microglia cells. In the present study, the effects of ADP on the intracellular calcium concentration ([Ca(2+)]i) in cultured dorsal spinal cord microglia were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescence indicator that could monitor real-time alterations of [Ca(2+)]i. Here we show that ADP (0.01-100 μM) causes a rapid increase in [Ca(2+)]i with a dose-dependent manner in cultured microglia. The action of ADP on [Ca(2+)]i was significantly blocked by MRS2211 (a selective P2Y13 receptor antagonist), but was unaffected by MRS2179 (a selective P2Y1 receptor antagonist) or MRS2395 (a selective P2Y12 receptor antagonist), which suggest that P2Y13 receptor may be responsible for ADP-evoked Ca(2+) mobilization in cultured microglia. P2Y13-evoked Ca(2+) response can be obviously inhibited by BAPTA-AM and U-73122, respectively. Moreover, removal of extracellular Ca(2+) (by EGTA) also can obvious suppress the Ca(2+) mobilization. These results means both intracellular calcium and extracellular calcium are potentially important mechanisms in P2Y13 receptor-evoked Ca(2+) mobilization. However, P2Y13 receptor-evoked Ca(2+) response was not impaired after CdCl2 and verapamil administration, which suggest that voltage-operated Ca(2+) channels may be not related with P2Y13-evoked Ca(2+) response. In addition, Ca(2+) mobilization induced by ADP was abolished by different store-operated Ca(2+) channels (SOCs) blocker, 2-APB (50 μM) and SKF-96365 (1 mM), respectively. These observations suggest that the activation of P2Y13 receptor might be involved in the effect of ADP on [Ca(2+)]i in cultured dorsal spinal cord microglia. Furthermore, our results raise a possibility that P2Y13 receptor activation causes Ca(2+) release from Ca(2+) store, which leads to the opening of SOCs.