Search

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.

The role of neuronal nitric oxide (NO) in the cerebrovascular response to partial seizures induced by intrahippocampal injection of kainate (KA) was investigated in mice deleted for the neuronal NO synthase gene (nNOS−/−) and in wild-type controls (WT). A second group of WT mice received the nNOS inhibitor, 7-nitroindazole (WT-7NI). Local cerebral blood flow (LCBF) was measured using the quantitative 14C-iodoantipyrine method. Within the epileptic focus, all three groups of seizing mice (WT, WT-7NI, and nNOS−/−) showed significant 26–88% LCBF increases in ipsilateral hippocampus, compared to saline-injected mice. Contralaterally to the epileptic focus, KA seizures induced a 21–47% LCBF decreases in hippocampus and limbic cortex of WT mice and in most contralateral brain structures of nNOS−/− mice, while WT-7NI mice showed no contralateral CBF change. Neuronal NO appears to be not involved in the cerebrovascular response within the epileptic focus, but may rather have a role in the maintenance of distant LCBF regulation during seizures.