Developmental expression of metabotropic P2Y(1) and P2Y(2) receptors in freshly isolated astrocytes from rat hippocampus

There are at least three subtypes of cloned metabotropic P2 receptors linke d to intracellular Ca2+ rises in rat brain cells, namely, P2Y(1), P2Y(2) an d P2Y(4). In this study we explore the subtypes of the metabotropic P2 rece ptors seen in freshly isolated astrocytes (FIAs) from P8-P25 rats. We found by single cell RT-PCR that in process-bearing FIAs from hippocampi of P8-P 12 rats, 31% of the glial fibrillary acidic protein (GFAP) mRNA (+) cells e xpressed P2Y(1) mRNA while only 5% of the cells tested expressed P2Y(2) mRN A. The expression of P2Y(1) receptor mRNA was not changed in FIAs from the hippocampi of P18-P25 rats, but 38% of the GFAP mRNA (+) cells in the P18-P 25 age group then showed P2Y(2) mRNA. We also studied whether the mRNA was expressing functional receptor protein by measuring Ca2+ responses to speci fic agonists for P2Y(1) and P2Y(2). We found that similar proportions of GF AP mRNA (+) FIAs responded to ATP or UTP as showed mRNAs for P2Y(1) and P2Y (2), respectively. Total tissue RNA from P9 and P24 rat hippocampus showed a 2.8-fold increase in P2Y(2) mRNA levels from P9 to P24 with a decrease in P2Y(1) mRNA. Thus, this study shows a marked up-regulation of mRNA for P2Y (2) from 9 to 24 days in rat hippocampus, and some of this increase is like ly due to the protoplasmic astrocytes which is being translated into functi onal receptor protein in these cells.