title: Carbamazepine-resistance in the epileptic dentate gyrus of human hippocampal slices.
abstract: Overexpression of drug efflux pumps at the blood brain barrier (BBB) has been suggested to be one important factor contributing to drug resistance in epilepsy. This would imply that resected brain tissue of drug-resistant patients is drug-sensitive in absence of the BBB. Here we studied the effects of carbamazepine (CBZ) at therapeutically relevant concentration on epileptiform activity electrophysiologically recorded in acute hippocampal slices of patients with mesial temporal lobe epilepsy (MTLE; 28 patients, 49 slices) or extra-hippocampal tumours (tumour; 6 patients, 11 slices). Epileptiform activity was induced by hilar stimulation (0.067 Hz) during elevation of extracellular potassium concentration ([K(+)](o)) and remained self-sustained in presence of 10-12 mM [K(+)](o). Quantitative analysis of data revealed that epileptiform activity in tissue of tumour-patients was predominantly suppressed by CBZ, indicating that the 'epilepsy model' used is CBZ-sensitive. In contrast, epileptiform activity in tissue of drug-resistant MTLE patients was resistant to CBZ in 82% of patients, partially suppressed in 11% and completely suppressed in 7%. The effects of CBZ in tissue of MTLE patients did not depend on the type of activity, hippocampal pathology, excitability of the tissue, or equilibration time of the drug. Considering that CBZ has direct access to all compartments of the slice, our results suggest that CBZ-resistance mechanisms are located within the parenchyma of the dentate gyrus and contribute to drug resistance in the majority of MTLE patients. BBB-located drug-resistance mechanisms per se may play a minor role in this region, because CBZ-sensitivity was only observed in 7% of CBZ-resistant patients.
authors.affiliation: Institute of Neurophysiology Berlin, Germany.
authors.forename: Katerina
authors.initials: K
authors.lastname: Jandová
authors.forename: Dennis
authors.initials: D
authors.lastname: Päsler
authors.forename: Leandro Leite
authors.initials: LL
authors.lastname: Antonio
authors.forename: Claudia
authors.initials: C
authors.lastname: Raue
authors.forename: Shengbo
authors.initials: S
authors.lastname: Ji
authors.forename: Marleisje
authors.initials: M
authors.lastname: Njunting
authors.forename: Oliver
authors.initials: O
authors.lastname: Kann
authors.forename: Richard
authors.initials: R
authors.lastname: Kovács
authors.forename: Heinz-Joachim
authors.initials: HJ
authors.lastname: Meencke
authors.forename: Esper A
authors.initials: EA
authors.lastname: Cavalheiro
authors.forename: Uwe
authors.initials: U
authors.lastname: Heinemann
authors.forename: Siegrun
authors.initials: S
authors.lastname: Gabriel
authors.forename: Thomas-Nicolas
authors.initials: TN
authors.lastname: Lehmann
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000927:Anticonvulsants / Q000008:administration & dosage*; D001812:Blood-Brain Barrier / Q000503:physiopathology; D001932:Brain Neoplasms / Q000503:physiopathology; D002220:Carbamazepine / Q000008:administration & dosage*; D018891:Dentate Gyrus / Q000187:drug effects*; D004334:Drug Administration Schedule; D004351:Drug Resistance / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D011188:Potassium / Q000378:metabolism; D013997:Time Factors
chemical_list: D000927:Anticonvulsants; D002220:Carbamazepine; D011188:Potassium