Characterization of the block of sodium channels by phenytoin in mouse neuroblastoma cells.

摘要: The interaction of phenytoin (DPH) with membrane ionic channels cultured N1E-115 neuroblastoma cells was studied. single suction pipette technique used for voltage clamp and intracellular perfusion. When the were held at -80 mV periods 1 min or more, DPH (20-100 microM) inhibited inward sodium current in a dose-dependent manner (resting block); resting block relieved by hyperpolarizing to -100 min. A shift slow inactivation curve Na induced can explain effect holding potential on block. fast curve, however, not affected. During repetitive pulsing DPH-induced inhibition enhanced (conditioned block). Conditioned both voltage- frequency-dependent. Conditioning pulses potentials which do appreciably open also produced conditioned block; prolongation conditioning even durations longer than time maximal steady-state progressively increased extent block, suggesting that interact inactivated closed channels. course recovery from voltage-dependent during slowed exhibited dependence. Recovery occurred faster when period more negative. We conclude blocks increasing fraction an state delaying transition but available This is depolarizing frequency stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)