title: A novel mechanism for the anticonvulsant effect of furosemide in rat hippocampus in vitro.
abstract: Though both in vivo and in vitro studies have demonstrated an anticonvulsant effect of the loop diuretic furosemide, the precise mechanism behind this effect is still debated. The current study investigates the effect of furosemide on Cs-induced epileptiform activity (Cs-FP) evoked in area CA1 of rat hippocampal slices in the presence of Cs(+) (5mM) and ionotropic glutamatergic and GABAergic receptor antagonists. As this model diverges in several respects from other epilepsy models it can offer new insight into the mechanism behind the anticonvulsive effect of furosemide. The present study shows that furosemide suppresses the Cs-FP in a dose-dependent manner with a near complete block at concentrations ≥ 1.25 mM. Because furosemide targets several types of ion transporters we examined the effect of more selective antagonists. Bumetanide (20 μM), which selectively inhibits the Na-K-2Cl co-transporter (NKCC1), had no significant effect on the Cs-FP. VU0240551 (10 μM), a selective antagonist of the K-Cl co-transporter (KCC2), reduced the ictal-like phase by 51.73 ± 8.5% without affecting the interictal-like phase of the Cs-FP. DIDS (50 μM), a nonselective antagonist of Cl(-)/HCO3(-)-exchangers, Na(+)-HCO3(-)-cotransporters, chloride channels and KCC2, suppressed the ictal-like phase by 60.8 ± 8.1% without affecting the interictal-like phase. At 500 μM, DIDS completely suppressed the Cs-FP. Based on these results we propose that the anticonvulsant action of furosemide in the Cs(+)-model is exerted through blockade of the neuronal KCC2 and Na(+)-independent Cl(-)/HCO3(-)-exchanger (AE3) leading to stabilization of the activity-induced intracellular acidification in CA1 pyramidal neurons.
authors: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
authors: Josiane
authors: J
authors: Uwera
authors: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
authors: Steen
authors: S
authors: Nedergaard
authors: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark. Electronic address: ma@biomed.au.dk.
authors: Mogens
authors: M
authors: Andreasen
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D002034:Bumetanide / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005665:Furosemide / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D018709:Statistics, Nonparametric; D013844:Thiazoles / Q000494:pharmacology; D013864:Thioglycolates / Q000494:pharmacology
chemical_list: D000927:Anticonvulsants; D002712:Chlorides; C572191:N-(4-methylthiazol-2-yl)-2-(6-phenylpyridazin-3-ylthio)acetamide; D049994:Sodium Potassium Chloride Symporter Inhibitors; D013844:Thiazoles; D013864:Thioglycolates; D002034:Bumetanide; D002586:Cesium; D005665:Furosemide; C028019:cesium chloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
keywords: Cl(−)/HCO(−)(3)-exchanger; Furosemide; KCC2; NKCC1; Seizure; pH(i)