AM-36 is a novel
neuroprotective agent incorporating both
antioxidant and Na(+) channel blocking actions. In cerebral ischaemia, loss of cellular ion homeostasis due to Na(+) channel activation, together with increased
reactive oxygen species (ROS) production, are thought to contribute to neuronal death. Since neuronal death in the penumbra of the ischaemic lesion is suggested to occur by apoptosis, we investigated the ability of
AM-36,
antioxidants and Na(+) channel antagonists to inhibit toxicity induced by the
neurotoxin,
veratridine in cultured cerebellar granule cells (CGC's).
Veratridine (10 - 300 microM) concentration-dependently reduced cell viability of cultured CGC's. Under the experimental conditions employed, cell death induced by
veratridine (100 microM) possessed the characteristics of apoptosis as assessed by morphology, TUNEL staining and
DNA laddering on
agarose gels. Neurotoxicity and apoptosis induced by
veratridine (100 microM) were inhibited to a maximum of 50% by the
antioxidants,
U74500A (0.1 - 10 microM) and U83836E (0.03 - 10 microM), and to a maximum of 30% by the Na(+) channel blocker,
dibucaine (0.1 - 100 microM). In contrast,
AM-36 (0.01 - 10 microM) completely inhibited
veratridine-induced toxicity ( IC(50) 1.7 (1.5 - 1.9) microM, 95% confidence intervals (CI) in parentheses) and concentration-dependently inhibited apoptosis. These findings suggest
veratridine-induced toxicity and apoptosis are partially mediated by generation of ROS.
AM-36, which combines both Na(+) channel blocking and
antioxidant activity, provided superior neuroprotection compared with agents possessing only one of these actions. This bifunctional profile of activity may underlie the potent
neuroprotective effects of
AM-36 recently found in a
stroke model in conscious rats.