Effects of droperidol on persistent sodium channel currents of pyramidal cell in hippocampal CA1 area of rats with cerebral ischemia / 中国组织工程研究

ABSTRACT

BACKGROUND: Both abnormal permeability of ionic channel and disturbance of ionic balance between inside and outside nerve cell are key factors for ischemic brain injury after ischemia. Depolarization induced by activation of sodium channel is starting link for cerebral ischemic injury.OBJECTIVE: To study the effects of droperidol on persistent sodium channel currents of pyramidal cell in hippocampal CA1 area of rats with cerebral ischemia with patch clamp technique so as to analyze whether droperidol can protect cerebral ischemic injury.DESIGN: Randomized controlled animal study.SETTING: Department of Anesthesiology of the Sixth People's Hospital Affiliated to Shanghai Jiaotong University and Department of Anesthesiology of the First People's Hospital Affiliated to Shanghai Jiaotong University.MATERIALS: The experiment was carried out at the Department of Anesthesiology of the First People's Hospital Affiliated to Shanghai Jiaotong University from April 2002 to April 2003. Totally 14 SD rats, aging 10-14days, without ablactation, were selected. Two cells in hippocampal CA1area of each rat were collected, totally 28 cells were divided into 4 groups:ischemic control group, 3 μmol/L droperidol group, 10 μmol/L droperidol group and 30 μmol/L droperidol group, with 7 cells in each group.METHODS: Pyramidal cells in hippocampal CA1 area were separated with digested enzyme method, and ischemic model of neuron was established through hypoxia and no sugar method. Cells were selected with the following conclusion criteria: well adherent wall, triangle or starry shape,bright soma, well refraction, obvious apophysis, steady plasma, and transparent nucleolus. Y-tube system was used for rapid medication. 3, 10 and 30 μmol/L droperidol were given to rats in 3, 10 and 30 μmol/L droperidols respectively, but rats in ischemic control group were not given any medicine. Whole-cell patch-clamp was used to recorded basic value of persistent sodium currents and changes of sodium channel currents during 3-minute and 5-minute ischemia.MAIN OUTCOME MEASURES: ① Record of normal persistent sodium current of neuron in cerebral hippocampal CA1 area; ② Record of persistent sodium current of neuron in cerebral hippocampal CA1 area during cerebral ischemia; ③ Effect of droperidol in various concentrations on persistent sodium current of neuron in cerebral hippocampal CA1 area during cerebral ischemia.RESULTS: Totally 28 cells in cerebral hippocampal CA1 area of 14 rats were entered the final analysis. ① Record of normal persistent sodium current of neuron in cerebral hippocampal CA1 area: 0.5 mmol/L CdCl2 calcium channel blocking agent and 20 mmol/L TEA kalium channel blocking agent were used to perform 400 ms square-wave stimulation under -105 mV claw voltage and -30 mV stimulated voltage. Introversion current,slight, late activation and lasting for a long time, was recorded and deter mined as persistent sodium currents by blocking toxin of puffer fish. ② Record of persistent sodium current of neuron in cerebral hippocampal CA1 area during cerebral ischemia: After 3-minute ischemia, persistent sodium currents in ischemic control group was increased as (1.60±0.21) times as that in normal group, and was (2.87 ±0.45) times after 5-minute ischemia. The difference was significant (P ＜ 0.05). ③ Effect of droperidol at various concentrations on persistent sodium current of neuron in cerebral hippocampal CA1 area during cerebral ischemia: Basic values of persistent sodium currents were (77.42±15.17) pA, (87.44±21.56) pA, (84.13±20.06) pA and (80.22±19.30) pA in ischemic control, 3, 10 and 30 μmol/L droperidol groups respectively, and the differences among groups were not significant. After 5-minute ischemia, values of persistent sodium currents were (105.36±17.16) pA, (94.74±18.88) pA and (84.88±13.94) pA in 3, 10 and 30 μmol/L droperidol groups respectively, which were obviously lower than that in the ischemic control group (218.31±29.34) pA.CONCLUSION: Persistent sodium currents increase under -105 mV claw voltage and -30 mV stimulated voltage during cerebral ischemic injury. Droperi dol can protect neuron by inhibiting the increase of persistent sodium current.