Binding of a peripheral benzodiazepine receptor ligand was used to quantify the reactive gliosis resulting from neuronal damage induced by systemic injections of kainic acid 7 days previously. The enhancement of binding in rat hippocampus could be prevented by injections of the purine analogue (R)-N6-phenylisopropyladenosine at 25 microgram/kg up to 2 h before or after the toxin. These results indicate that the purine is able to prevent neurotoxicity by interrupting events occurring some time after kainate administration.