Electrophysiological and pharmacological properties of the human brain type IIA Na+ channel expressed in a stable mammalian cell line.
The human brain voltage-gated Na+ channel type IIA alpha subunit was cloned and stably expressed in Chinese hamster ovary cells and its biophysical and pharmacological properties were studied using whole-cell voltage-clamp. Fast, transient inward currents of up to -8,000 pA were elicited by membrane depolarization of the recombinant cells. Channels activated at -50 mV and reached maximal activation at -10 mV to 0 mV. The reversal potential was 62 +/- 2 mV which is close to the Na+ equilibrium potential. The half-maximal activation and inactivation voltages were -24 +/- 2 mV and -63 +/- 1 mV, respectively. Currents were reversibly blocked by tetrodotoxin with a half-maximal inhibition of 13 nM. The effects of four commonly used anti-convulsant drugs were examined for the first time on the cloned human type IIA channel. Lamotrigine and phenytoin produced concentration- and voltage-dependent inhibition of the type IIA currents, whereas, sodium valproate and gabapentin (up to 1 mM) had no effect. These results indicate that recombinant human type IIA Na+ channels conduct tetrodotoxin-sensitive Na+ currents with similar properties to those observed in recombinant rat brain type IIA and native rat brain Na+ channels. This stable cell line should provide a useful tool for more detailed characterization of therapeutic modulators of human Na+ channels.
Xie
X
X
Neurosciences Unit, GlaxoWellcome, Medicines Research Centre, Stevenage, Herts, UK.
Dale
T J
TJ
John
V H
VH
Cater
H L
HL
Peakman
T C
TC
Clare
J J
JJ
D000818:Animals; D001923:Brain Chemistry; D016466:CHO Cells; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D004553:Electric Conductivity; D004594:Electrophysiology; D015870:Gene Expression; D006801:Humans; D000077213:Lamotrigine; D018408:Patch-Clamp Techniques; D010672:Phenytoin / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics* / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014162:Transfection; D014227:Triazines / Q000494:pharmacology
D011994:Recombinant Proteins; D015222:Sodium Channels; D014227:Triazines; D013779:Tetrodotoxin; D010672:Phenytoin; D000077213:Lamotrigine