Hydrolysis of polyphosphoinositides in astrocytes by platelet-activating factor

In primary astrocyte cultures, picomolar concentrations of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) evoked the formation of inositol phosphates (InsP), including inositol trisphosphate. This effect was not observed with the biologically inert lyso-PAF, nor in cells pretreated with phorbol myristate acetate to downregulate receptors. PAF at concentrations greater than or equal to 10(-9) M did not elevate InsP, suggesting some form of uncoupling of the receptor from phospholipase C. The responsiveness of astrocytes to PAF is further evidence for the role of these cells in the central nervous system response to trauma.