Expression of P2X receptors on rat microglial cells during early development

We have used single- and double-labeling immunfluorescence and reverse transcription-polymerase chain reaction (RT-PCR) methods to examine expression of P2X receptor subtypes on microglial cells of brain in late embryonic and postnatal rat, in the N9 microglial cell line and primary cultured microglial cells. P2X(1), P2X(4), and P2X(7) receptors were shown on microglial cells from late embryonic day 16. Almost all the microglial cells that were positive for the marker ED1, expressed P2X(1) and P2X(4) receptors, whereas only about 30% of the cells with EDI-immunoreactivity were found to express the P2X(7) receptor. Positive cells were localized mainly in the white matter and around ventricles. From postnatal day 7, many microglial cells with P2X(4) receptor-immunoreactivity were seen around the blood vessels. At postnatal day 30, microglial cells with P2X(1) receptor-immunoreactivity disappeared and the cells with P2X(4) receptor-immunoreactivity were mainly localized around blood vessels and lining the subarachnoid space. From postnatal day 30, the microglial cells with P2X(7) receptor-immunoreactivity were found to be distributed widely in the fore-brain. Cells with P2X(7) receptor-immunoreactivity from P30 were not labeled by ED1, but some were labeled by isolectin B4. The expression of P2X(1), P2X(4), and P2X(7) receptor mRNA and protein on primary cultures of rat microglial cells and on the N9 microglial cell line was demonstrated with immunocytochemistry and RT-PCR. This is the first report that the P2X(1) receptor is expressed on microglial cells, at least in early development, before postnatal day 30. (c) 2005 Wiley-Liss, Inc.