Neuroprotective effects of a dihydropyridine derivative, 1,4-dihydro- 2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 6-(5- phenyl-3-pyrazolyloxy)hexyl ester (CV-159), on rat ischemic brain injury

CV-159, 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5- pyridinedicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy)hexyl ester, is a dihydropyridine derivative that blocks the L-type Ca²⁺ channel and inhibits the calmodulin (CaM)-dependent pathway. In this study, we examined the effects of CV-159 on rat ischemic brain injury. CV-159 (5 and 10 mg/kg, p.o.) gave significant protection against delayed neuronal death in the hippocampal CA1 region after 15-min transient forebrain ischemia. In contrast, the Ca²⁺ antagonists nicardipine (1 and 10 mg/kg, p.o.) and nifedipine (1 mg/kg, i.p.) and the CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W- 7, 500 ng, i.c.v.) had no effect on this hippocampal neuronal death. CV-159 also diminished the size of the brain infarct after permanent middle cerebral artery (MCA) occlusion, although physiological variables, including regional cerebral blood flow, were not affected. The increase in the water content of the infarcted cortex induced by MCA occlusion was significantly reduced by CV-159. On the other hand, neither nicardipine nor nifedipine affected the brain infarct size, volume or increased water content induced by MCA occlusion, as previously reported (A. Sauter and M. Rudin, Am. J. Hypertens. 4 121S-127S, 1991). These findings indicate that Ca²⁺ antagonists, such as nicardipine and nifedipine, and W-7 have no effect on rat ischemic brain injury. The results suggest that CV-159 protects against ischemic brain injury. This might be mediated by both blocking the L-type Ca²⁺ channel and inhibiting CaM-dependent function via Ca²⁺/CaM binding at a different binding site from that of W-7 to CaM (H. Umekawa, K. Yamakawa, K. Nunoki, N. Taira, T. Tanaka, and H. Hidaka, Biochem. Pharmacol. 37 3377-3381, 1988).