title: Carbonic anhydrase inhibitor sulthiame reduces intracellular pH and epileptiform activity of hippocampal CA3 neurons.
abstract: OBJECTIVE
  Sulthiame is a carbonic anhydrase (CA) inhibitor with an anticonvulsant effect in the treatment of benign and symptomatic focal epilepsy in children. The aim of the study was to elucidate the mode of action of sulthiame with respect to possible changes of intracellular pH (pHi) that might develop along with sulthiame's anticonvulsant properties.
  
  
  METHODS
  The effects of sulthiame (a) on pHi of 2',7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein-acetoxymetyl ester (BCECF-AM) loaded CA3 neurones as well as (b) on epileptiform activity (induced by 50 microM 4-aminopyridine) were compared with those of the CA inhibitors acetazolamide and benzolamide.
  
  
  RESULTS
  In the majority of neurons, sulthiame (1.0-1.5 mM; n = 8) as well as the membrane permeant acetazolamide (0.5-1.0 mM; n = 6) reversibly decreased pHi by 0.18 +/- 0.05 (SD) and 0.17 +/- 0.10 (SD) pH units, respectively, within 10 min. The poor membrane permeant benzolamide (1.0-2.0 mM) had no influence on pHi (n = 8). Sulthiame (1.0-2.5 mM) and acetazolamide (1.0-2.0 mM) reversibly reduced the frequency of action potentials and epileptiform bursts after 10-15 min (n = 9, n = 7), whereas benzolamide (1.0-2.0 mM) had no effect (n = 6).
  
  
  CONCLUSIONS
  The results suggest that sulthiame acts as a membrane-permeant CA inhibitor whose beneficial effect on epileptiform activity results at least in part from a modest intracellular acidosis of central neurons.
authors.affiliation: Department of Neurology, University of Essen, Essen, Germany. tobias.lenger@uni-essen.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Leniger
authors.forename: Martin
authors.initials: M
authors.lastname: Wiemann
authors.forename: Dieter
authors.initials: D
authors.lastname: Bingmann
authors.forename: Guido
authors.initials: G
authors.lastname: Widman
authors.forename: Andreas
authors.initials: A
authors.lastname: Hufnagel
authors.forename: Udo
authors.initials: U
authors.lastname: Bonnet
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001574:Benzolamide / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology*; D004827:Epilepsy / Q000378:metabolism / Q000517:prevention & control*; D006168:Guinea Pigs; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D013843:Thiazines / Q000494:pharmacology*; D000096926:Benzenesulfonamides
chemical_list: D000086:Acetazolamide; D000927:Anticonvulsants; D001574:Benzolamide; D002257:Carbonic Anhydrase Inhibitors; D013843:Thiazines; C084593:sulthiame; D000096926:Benzenesulfonamides