title: Phenytoin and carbamazepine: differential inhibition of sodium currents in small cells from adult rat dorsal root ganglia.
abstract: We determined the effects of carbamazepine and phenytoin, anticonvulsant drugs used to treat neuropathic pain, on the heterogeneous population of Na+ channels in patch-clamped small cells from adult rat dorsal root ganglia. Both fast tetrodotoxin-sensitive (TTX-S) and slow TTX-resistant (TTX-R) currents were inhibited by 10-100 microM drug. TTX-R currents were divided into two classes. Control type I currents had a very depolarized voltage for 50% availability (Vh) of ca. -29 mV and 17% reduction in current by the 20th pulse at 1 Hz. Control type II currents had a Vh closer to -46 mV and 49% reduction in current at 1 Hz. At 0.1 Hz, which gave relatively little loss of control current, 100 microM drug caused 53 +/- 4% (n = 5) block of type I current and 88 +/- 2% inhibition of type II current (n = 4). Strong 1 s hyperpolarizing prepulses relieved most of the fast channel block but had much less effect on blocked TTX-R channels.
authors.affiliation: Department of Anatomy and Physiology, University of Dundee, UK.
authors.forename: A M
authors.initials: AM
authors.lastname: Rush
authors.forename: J R
authors.initials: JR
authors.lastname: Elliott
mesh_terms: D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D002220:Carbamazepine / Q000494:pharmacology*; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010672:Phenytoin / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000927:Anticonvulsants; D026941:Sodium Channel Blockers; D002220:Carbamazepine; D013779:Tetrodotoxin; D010672:Phenytoin