Effects Of Lead On Potassium Channels In Rat Hippocampal Neurons

Part one: Study on the method and the records of potassium currents of acutely isolated hippocampal neuron in ratThe hippocampal neurons were isolated by enzymatic and mechanical methods from 10-15 day postnatal rat, and its activity were verified by morphology. Results showed that single hippocampal neuron with good shape characteristic can be obtained by using this method.Several kinds of potassium currents were recorded in acutely isolating rat hippocampal neurons using whole-cell patch clamp technique, including voltage-depedent potassium current, delayed-rectifier potassiumcurrent, ATP-sensitive potassium current and hyperpolarization-activated current. Voltage-depedent potassium current and delayed-rectifier potassium current can be confirmed according to the electrophysiological properties and effects of TEA-Cl and 4-AP. This proved that the method can maintain the activity of ion channels in rat hippocampal neurons, and it has important value for deeply research the effects of drugs and toxins on hippocampal ion channels and on its signal transduction mechanism.Part two: Effects of Pb~2+ on potassium channels in acutely isolated rat hippocampal neuronsThe effects of Pb~2+ on voltage-depedent potassium currents were studied in acutely isolated hippocampal neurons from rat using the patch-clamp technique in the whole-cell configuration. Our results demonstrate that Pb~2+ in micromolar concentration can reversible block potassium currents and make the current-voltage relation shift to positive potentials in a voltage-dependent, dose-depedent manner. Voltage-depedent potassium currents (I_K) were inhibited by 7.97±2.65%, 19.08±3.12%, 40.99±5.09% with 1, 10, 100μmol/L Pb~2+ respectively. Delayed-rectifier potassium currents (I_KDR) were inhibited by 8.20±4.29%, 23.59±4.66%, 47.99±10.94% with 1,10,100μmol/L Pb~2+ respectively.Part three: Effects of Pb~2+ on potassium channels in cultured rathippocampal neuronsWe have used the patch-clamp method in the whole-cell configuration to investigate the effects of Pb~2+ on the outward potassium current (I_k), delayed-rectifier potassium current (I_kdr), and transient outward potassium current(IA) in cultured rat hippocampal neurons. The results demonstrate Pb2+ in micromolar concentration was a dose- and voltage-depedent blocker of I_K, I_KDR and I_A.As a whole, we investigated the effects of Pb on the potassium channels in acutely isolated and cultured rat hippocampal neurons. The binding site would be near the pore of channels or the inner of channels. These effects has to be taken into consideration as a possible contributing mechanism for the neurological symptoms of enhanced brain activity and the impairment of learning and memory seen during intoxication.