T-477, a novel Ca²⁺- and Na⁺ channel blocker, prevents veratridine-induced neuronal injury

To evaluate the effect of (R)-(+)-2-(4-chlorophenyl)-2,3-dihydro-4-diethyl aminoacetyl-4H-1,4-benzothiazine hydrochloride (T-477), a novel Na⁺- and Ca²⁺ channel blocker, on neuronal injury in vitro, we studied veratridine-induced injury in cultured rat hippocampal neurons. Neurons swelled extensively 10 min after the addition of veratridine, and returned to their initial size within 2 h. Intracellular Na⁺ and Ca²⁺ concentrations and amino acid release from the cells, in particular, that of glutamate, increased after the treatment with veratridine. Approximately 70% of neurons died within 24 h. T-477 inhibited both veratridine-induced swelling and death in a concentration-dependent manner. Moreover, T-477 concentration dependently reduced the increases in Na⁺ and Ca²⁺ influx and amino acid release. These results suggest that T-477 prevented the veratridine-induced influx of Na⁺ and, thereby, reduced neuronal swelling. This, combined with the effects of T-477 on the inhibition of Ca²⁺ influx and glutamate release, possibly by the blockade of Na⁺ channels, may be the mechanism by which T-477 protects neurons from death induced by veratridine. Copyright (C) 2000 Elsevier Science B.V.