P2X7 receptors, but not P2Y purine/pyrimidine receptors, are strongly coupled to protein kinases associated with growth arrest. Quiescent cultures of rat cortical astrocytes were treated with UTP (100 uM) or BzATP (100 uM) for the times indicated, Cells were lysed and stimulation of phosphorylation of p38/MAPK and SAPK were determined by immunoblotting as described in Materials and Methods. A representative blot is shown in A. In B, group data of ratios of phosphorylated to total p38/MAPK and SAPK are shown (n = 4). BzATP stimulated phosphoryation of both p38/MAPK and SAPK more strongly than UTP at 15 and 30 min (*, p< 0.05).