A novel Na+/Ca2+ channel blocker, NS-7, suppresses hypoxic injury in rat cerebrocortical slices

Abstract

The substance 4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy) pyrimidine hydrochloride (NS-7) has been developed recently as a cerebroprotective compound with Na⁺ and Ca²⁺ channel blocking action. In the present study, the effect of NS-7 in an in vitro model of hypoxic injury was examined and the possible involvement of Na⁺ and Ca²⁺ channels in the hypoxic injury subsequently determined. When slices of rat cerebral cortex were exposed to hypoxia/glucose deprivation followed by reoxygenation and restoration of the glucose supply, marked leakage of lactate dehydrogenase (LDH) occurred 3–6 h after reoxygenation. This hypoxia/reoxygenation-induced injury was blocked almost completely by the removal of extracellular Ca²⁺ or by chelating intracellular Ca²⁺ with 1,2-bis(o-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid tetra(acetoxymethyl)ester (BAPTA/AM). In addition, combined treatment with the N-type Ca²⁺ channel blocker ω-conotoxin GVIA and the P/Q-type Ca²⁺ channel blocker ω-agatoxin IVA significantly reduced LDH leakage, although neither of these Ca²⁺ channel blockers alone, nor nimodipine, an L-type Ca²⁺ channel blocker, was effective. On the other hand, several Na⁺ channel blockers, including tetrodotoxin, local anaesthetics and antiepileptics, significantly reduced the hypoxic injury. NS-7 (3–30 µM) concentration-dependently inhibited LDH leakage caused by hypoxia/reoxygenation, but had no influence on the reduction of tissue ATP content and energy charge during hypoxia and glucose deprivation. It is suggested that blockade of Na⁺ and Ca²⁺ channels is implicated in the cerebroprotective action of NS-7.