Local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) were studied by autoradiographic techniques in indomethacin- and ibuprofen-treated rats with focal cortical freezing lesions. Widespread depression of LCGU, which developed with time after the lesion in untreated animals was significantly diminished by the prostaglandin synthetase inhibitors indomethacin (single injection 7.5 mg/kg) and ibuprofen (36 mg/kg/day). Both drugs were effective when given 6 h before or up to 24 h after the lesion was made. The effect of the drugs was most striking in cortical areas of the traumatized hemisphere, where the depression was most profound in untreated animals. Thus, 3 days after the lesion, average LCGU in these regions was 46%, 86%, and 98% of normal in untreated, indomethacin-pretreated, and ibuprofen-pretreated rats, respectively. Prostaglandin formation was completely inhibited in the lesion area in the indomethacin-treated rats (PGF2 alpha 1.8 ng/g, compared to 57.5 ng/g in untreated and 1.4 ng/g in nonlesioned animals). The results suggest that some components of the prostaglandin system are involved in mechanisms underlying a widespread depression in functional state of the rat brain that develops in response to injury. In control animals, indomethacin was shown to have a biphasic effect on LCBF, an early depression shown previously by others followed at 24 h by a considerable increase.