[Effects of melatonin on the voltage-gated delayed rectifier potassium channels of cultured hippocampal neurons of new-born rats].

Objective To investigate the effects of melatonin on vohage-gated delayed rectifier potassium channels.Methods Hippocampus neurons were obtained from newborn Wistar rat and cultured.Primary cuhured for 7 to 12 days of new-born Wistar rat were selected as objectives.Patch clamp whole-cell recording technique was used on the hippocampus neurons cultured for 7 to 12 day.to record the delaved rectifier potassium current to analyze the basic electrophysiological characteristics.The effects of melatonin of the concentmtions of 1 nmol/L,10 nmol/L,100 nmol/L,1 mol/L,10 mol/L,100 mol/L,and 1 mmol/L on the amplitudes and kinetics of delayed rectifier potassium currents were investigated.Results With different vohage protocols and specific blockers of potassium channel(4-AP and TEA) a delayed rectifier potassium current that activated and inactivated slowly and had the outward rectifying characteristics (Ik) from the outward potassium currents in cultured new-born hippocampus neurons was separated.The effect of melatonin on the delayed rectifier channel was rapid,reversible and voltage-dependent. Melatonin had no effect on the kinetic characteristics of the Ⅰ-Ⅴ curve. Melatonin increased the potassium current concentmtion-dependently. 1 - 100 nmol/L melatonin increased the amplitude of potassium current gradually;the effects of 1-100 μmol/L melatonin on the potassmm current increased concentration-dependently,while the action of 1 mmol/L melatonin decreased.Conclusion Melatonin reversibly increases the rectifier delayed potassium currents of the cultured hippocampus neurons of new-born rat.This may be involved in some aspects of physiological and pathological significance of potassium currents. Key words: Melatonin; Hippocampus;  Neurons;  Rectifier delayed potassium channel