Abstract:Neuronal cell death as a result of apoptosis is associated with cerebrovascular stroke and various neurodegenerative disorders. Pharmacological agents that maintain normal intracellular Ca 2ϩ levels and inhibit cellular oxidative stress may be effective in blocking abnormal neuronal apoptosis. In this study, a spontaneous (also referred to as age-induced) model of apoptosis consisting of rat cerebellar granule cells was used to evaluate the antiapoptotic activities of voltage-sensitive Ca 2ϩ channel blockers and various antioxidants. The results of these experiments demonstrated that the charged, dihydropyridine Ca 2ϩ channel blocker amlodipine had very potent neuroprotective activity in this system, compared with antioxidants and neutral Ca 2ϩ channel blockers (nifedipine and nimodipine). Within its effective pharmacological range (10 -100 nM), amlodipine attenuated intracellular neuronal Ca 2ϩ increases elicited by KCl depolarization but did not affect Ca 2ϩ changes triggered by N-methyl-D-aspartate receptor activation. Amlodipine also inhibited free radical-induced damage to lipid constituents of the membrane in a dose-dependent manner, independent of Ca 2ϩ channel modulation. In parallel experiments, spontaneous neuronal apoptosis was inhibited in dose-and time-dependent manners by antioxidants (U-78439G, ␣-tocopherol, and melatonin), nitric oxide synthase inhibitors (N-nitro-L-arginine and N-nitro-D-arginine), and a nitric oxide chelator (hemoglobin) in the micromolar range. These results suggest that spontaneous neuronal apoptosis is associated with excessive Ca 2ϩ influx, leading to further intracellular Ca 2ϩ increases and the generation of reactive oxygen species. Agents such as amlodipine that block voltage-sensitive Ca 2ϩ channels and inhibit cellular oxidative stress may be effective in the treatment of cerebrovascular stroke and neurodegenerative diseases associated with excessive apoptosis.

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