Abstracts

Rationale: The normal function of GABA_A receptor-mediated inhibition crucially depends upon the chloride gradient across the membrane. The gradient is governed by the operation of cation coupled chloride transporters, which are altered in human epilepsy. To evaluate links between impaired transporters and the severity of seizure activity, we quantified neuronal properties and correlated them with different clinical parameters including type and frequency of seizures. Methods: Experiments were approved by the Ethics Committee and patients provided informed consent to use the tissue for research. Human neocortical tissues from epilepsy surgery were investigated in vitro with intracellular sharp microelectrode recordings using standard procedures. The electrodes were filled with either 1 M potassium acetate or 1 M KCl. Synaptic properties were evaluated with input-output relationships. The kinetics of chloride extrusion was determined from changes of the peak amplitudes of IPSP_A following iontophoretic chloride injections. We related the cellular data, averaged for each resection, to clinical parameters, including duration of epilepsy, the documented annual numbers of auras, complex partial seizures (CPS) and grand maux (GM). The clinical data were segregated as follows: duration of epilepsy