P2Y1Purinoceptor-Mediated Ca2+Signaling and Ca2+Wave Propagation in Dorsal Spinal Cord Astrocytes

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Abstract
ATP is known to act as an extracellular messenger mediating the propagation of Ca2+waves in astrocyte networks. ATP mediates Ca2+waves by activating P2Y purinoceptors, which mobilize intracellular Ca2+in astrocytes. A number of P2Y purinoceptor subtypes have been discovered, but it is not known which P2Y subtypes participate in transmitting astrocyte Ca2+waves. Here, we show that ATP analogs that are selective agonists for the P2Y1subtype of purinoceptor caused release of intracellular Ca2+in astrocytes from the dorsal spinal cord. The Ca2+responses were blocked by adenosine-3′-phospho-5′-phosphosulfate, an antagonist known to selectively inhibit P2Y1but not other P2Y purinoceptor subtypes. Also, we show that P2Y1mRNA is expressed in dorsal spinal cord astrocytes. Furthermore, expression of P2Y1in an astrocytoma cell line lacking endogenous purinoceptors was sufficient to permit propagation of intercellular Ca2+waves. Finally, Ca2+wave propagation in dorsal spinal cord astrocytes was suppressed by pharmacologically blocking P2Y1purinoceptors. Together, these results indicate that dorsal spinal astrocytes express functional P2Y1purinoceptors, which participate in the transmission of Ca2+waves. Ca2+waves in astrocytes have been implicated as a major signaling pathway coordinating glial and neuronal activity; therefore, P2Y1purinoceptors may represent an important link in cell–cell signaling in the CNS.