Role of endothelial nitric oxide synthase in cerebral blood flow changes during kainate seizures: A genetic approach using knockout mice

The role of endothelial nitric oxide (NO) in the cerebrovascular response to partial seizures was investigated in mice deleted for the endothelial NO synthase gene (eNOS−/−) and in their paired wild-type (WT) congeners. Local cerebral blood flow (LCBF, quantitative [14C]iodoantipyrine method) was measured 3–6 h after unilateral kainate (KA) injection in the dorsal hippocampus; controls received saline. In WT mice, KA seizures induced a 22 to 50% LCBF increase restricted to the ipsilateral hippocampus, while significant LCBF decreases (15–33%) were noticed in 22% of the contralateral areas, i.e., the parietal cortex, amygdala and three basal ganglia areas, compared to saline-injected WT mice. In eNOS−/− mice, no LCBF increases were recorded within the epileptic focus and generalized contralateral LCBF decreases (22–46%) were noticed in 2/3 of the brain areas, compared to saline-injected eNOS−/− mice. Thus, endothelial NO is the mediator of the cerebrovascular response within the epileptic focus and participates in the maintenance of LCBF in distant areas.