RESUMEN
BACKGROUND: Electrical activity of nerve cells is based on the ion channel activity on cell membrane. Epilepsy is basically characterized by abnormal neuronal discharge. The foundation is ion channel activation on cell membrane and ion transmembrane movement, however, whether Ca2+-activated K+ channel involves in epilepsy induced by Coriaria Lactone is still unclear.OBJECTIVE: Considering rat hippocampal pyramidal neurons as target,we investigate the effect of Coriaria Lactone on neuronal Ca2+-activated K+ channels in epilepsy induced by Coriaria Lactone.DESIGN: Randomized controlled experimental trials.SETTING: Department of Neurology, West China Hospital, Sichuan University and Institute. of Myocardium Electrophysiology of Luzhou Medical College.MATERIALS: This experiment was carried out in Luzhou Medical College, Sichuan Province, from May to December 2000. Totally 100 Wistar infant rats within 24-hour ages were selected.METHODS: Wistar infant rats were anaesthetized and its hippocampus was obtained under disinfected state, pyramidal neurons were cultured for 7-10 days, neurons growing well with typical shape model were colleted normal control group, 19 dishes were added with DMEM culture medium,given different membrabe voltage and then followed by adding in te3 subgroups with 8 dishes each one. Added seperately DMEM culture medium containing f0-8, 10-7, 10~ mol/L concentration of calcium ion, and 2.0 mL/L Coriaria Lactone induced epilepsy group: added with DMEM culture medium with different dosages of Coriaria Lactone and finally tetraethylamine in each concentration of 26 dishes for totally 130 dishes.Cell-attache method and inside-out method of patch-clamp technique were used to record the neuronal single channel electricity. The open probability, average opening hour and closing hour, electric current amplitude of channel were analyzed.activated K+ channels of pyramidal neurons at normal, various membrane To observe and record the influence of Coriaria Lactone on the activation of pyramidal neuronal cell membrane, as well as the role of tetraethylamine.were only small amount of pyramidal neurons randomly opening its Ca2+-activated K+ channels and it displayed obvious voltage-dependent property.The channel electric conductance was (122.79±21.68) pS. The channels the inside-out condition, Ca2+-activated K+ channel displayed calcium iondependent property. The average opening rate was 0.022±0.006, 0.040±0.007, 0.142±0.049 when the calcium concentration was 10-8, 10-7,aria Lactone could increase the opening rate of Ca2+-activated K+ channels when the free calcium ion in bath solution was 10-8 mol/L and memLactone, 1.0 mL/L Coriaria Lactone could increase the average opening time of Ca2+-activated K+ channels (1.867±0.210, 6.900±0.120, P ＜ 0.01), and reducing the average closing time (78.505±7.192,6.233±0.854, P ＜ 0.01).CONCLUSION: In epilepsy induced by Coriaria Lactone, the activation of Ca2+-activated K+ channels might play an important role of negative modulation.
RESUMEN
BACKGROUND: Abnormal neuronal discharge arose from the activation of cell membrane ion channels and transmembrane ion transport. The electric activity of the cells is associated with cell metabolism fundamentally through adenosine triphosphate (ATP)-sensitive potassium(KATP) channels.Currently the involvement of KATP channels in the pathogenesis of epilepsy and the regulation of KATP channels by coriaria lacton (EL) remain unknown.OBJETCIVE: To investigate the changes of cell membrane KATP channels in rat hippocampal neurons in response to CL as an epilepsy-inducing agent, and explore the role of KATP channels in the pathogenesis of epilepsy.DESIGN: Randomized controlled experiment.SETTING: Department of Neurology, West China Hospital Affiliated to Sichuan University, and Teaching and Research Section of Physiology,West China College of Preclinical Medicine and Forensic Medicine of Sichuan University.MATERIALS: This experiment was carried out at Luzhou Medical College between May and December 2000. Hippocampus pyramidal neurons were obtained from neonatal Wistar rats and randomized into normal control group, tetraethylammonium chloride (TEA) group, DNP group, CL group, and electric conductance and dynamics group.METHODS: The hippocampus of newborn Wistar rats was separated under aseptic condition and cultured for 24 hours prior to treatment with 10 μmol/L cytarabine for selective cell culture for 7-10 days. The cells in good growth exhibiting typical morphology of pyramidal neurons were then selected for patch-clamp experiment. The cells in the normal control group were treated with normal saline, which was replaced by 5 mmol/L TEA in TEA group, by 30 μmol/L DNP then 0.5 mol/L ATP in DNP group, and by 1.0 mL/L CL then 1 μmol/L glibenclamide in CL group. In electric conductance and dynamics group, the clamp voltage was firstly adjusted to investigate the channel opening before CL was added to the cells.MAIN OUTCOME MEASURES: ① Activity and curve of neuronal KATP channels; ② Effects of various clamp voltages on the channels activity and the effects of interventions with DNP, ATP and TEA; ③ Activation of neuronal membrane KATP channels induced by CL and the influence of glibenclamide.RESULTS: The reversal potential of the channels approximated 0 mV in homologous high-potassium solution. The opening of KATP channels increased along with the absolute value of the clamp voltage in a voltage-dependent manner, which was blocked by TEA. The electric current-voltage (Ⅰ-Ⅴ)curve could be fitted to a straight line with the electric conductance of (78.23±12.04) pS. Administration of 30 μmol/L DNP enhances the opening of the channels, which could be suppressed by 0.5 mol/L ATP.Addition of 1.0 mL/L CL to the cells caused obviously increased channel opening, which was suppressed by 1 μmol/L glibenclamide. The channel opening time was (1.754±0.060) ms for epileptic neuron τ01and (1.733±0.046) ms for normal neurons, showing no significant difference between them (n=25, t=0.147, P ＞ 0.05), but compared with the channel opening time of (2.441±0.265) ms for τ02 normal neurons, and duration was significantly prolonged in the epileptic neurons to reach (10.446±0.579)ms (n=25, t=0.000, P ＜ 0.01).CONCLUSION: The opening of KATP channels is responsible for reducing the action potential frequency for neuronal protection, which might be a negative feedback mechanism.