Zonisamide enhances slow sodium inactivation in Myxicola.
In voltage-clamped Myxicola giant axons Zonisamide (1,2-benzisoxazole-3-methanesulfonamide) caused a hyperpolarizing shift in the steady-state fast inactivation curve and retarded recovery from fast and slow Na+ inactivation. The effects of Zonisamide on steady-state fast inactivation could be described assuming a single binding site with a dissociation constant of 12 microM. Slow inactivation was significantly more sensitive, with a Kd of 1 microM from both steady-state and kinetic data. While these results account for anticonvulsant activity, the differential sensitivity suggests Zonisamide may also be useful in studies of the slow inactive state of the Na+ channel.
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D001369:Axons / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects*; D007555:Isoxazoles / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D010080:Oxazoles / Q000494:pharmacology*; D011077:Polychaeta; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D000078305:Zonisamide
D000927:Anticonvulsants; D007473:Ion Channels; D007555:Isoxazoles; D010080:Oxazoles; D000078305:Zonisamide; D012964:Sodium; D011188:Potassium