Rufinamide is a structurally novel, antiepileptic drug approved for the treatment of Lennox-Gastaut syndrome.
Its mechanism of action involves inhibition of voltage-gated Na+ channels (VGSCs) with possible membrane-stabilizing
effects. VGSCs play a significant role in the pathogenesis of neuropathic pain. Therefore, we investigated the effects of
rufinamide on tetrodotoxin-resistant sodium current (TTX-R INa) in acutely dissociated rat dorsal root ganglion (DRG)
neurons isolated from streptozotocin-induced diabetic rats by using whole-cell voltage-clamp configuration. In addition,
the functional and behavioural nociceptive parameters were evaluated to assess its potential in diabetic neuropathy. Diabetic
rats demonstrated the mechanical allodynia and thermal hyperalgesia with reduced nerve perfusion and conduction
velocity as compared to control. Rufinamide treatments (3 and 10 mg/kg) significantly improved these functional and nociceptive
deficits. Diabetic rat DRG neurons exhibited increased TTX-R INa density as compared to control. The voltagedependent
activation and steady-state inactivation curves for TTX-R INa in DRG neurons from diabetic rats were shifted
negatively as compared to control. Rufinamide treatments significantly blocked the TTX-R Na+ channel activity as evident
from significant reduction in INa density and hyperpolarizing shift in activation and inactivation curves as compared
to diabetic control. This suggests that rufinamide acts on TTX-R Na+ channels, reduces channel activity and attenuates
nerve functional and behavioral parameters in diabetic rats. Altogether, these results indicate therapeutic potential of rufinamide
in the treatment of diabetic neuropathy.
Keywords: Diabetic neuropathy, dorsal root ganglion, rufinamide, voltage-gated sodium channel, whole-cell patch-clamp.
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