REGIONAL DIFFERENCE IN NITRIC-OXIDE PRODUCTION DURING FOREBRAIN ISCHEMIA

The hippocampus has been shown to exhibit particular vulnerability to ischemia, suggesting the existence of inherent processes leading to ne uronal death. Nitric oxide (NO) has been implicated in neurotoxicity d ue to ischemia. The relationship between regional distribution of NO s ynthesis induced by ischemia and the areas vulnerable to ischemia rema ins elusive. In the present study, we explored regional variation in N O synthesis by determining the concentrations of nitrite (NO2-), a maj or metabolite of NO, in the brain in vivo microdialysis samples obtain ed from the hippocampus and the striatum subjected to ischemia. Spragu e-Dawley rats were anesthetized with pentobarbital (40 mg/kg, i.p.). A n in vivo microdialysis probe was implanted into the hippocampus or th e striatum. Subsequently, the animals were subjected to forebrain isch emia for 20 min by occlusion of both common carotid arteries and induc ed hypotension. Forebrain ischemia gave rise to a significant change i n NO2- level only in the hippocampus, resulting in an increase to 111. 2 +/- 5.4 (mean +/- SEM) % of the preischemia level. This finding sugg ests the presence of a regional difference in NO production during isc hemia, which may be concerned with the underlying mechanism of ischemi c vulnerability. (C) 1997 Academic Press.