| [Objective]With the wide use of power and electronics, model wireless communication, people made more attention on the electromagnetic radiation, especially on the low frequency electromagnetic fields. Organisms nerve, visual, endocrine, cardiovascular will be impacted when touching with power frequently. The nervous system takes an important place in the human’s daily information acceptance and transmission. Therefore, it is essential to study electrophysiological activity of nerve cells. The key research points of this paper are the effects of0.5mT power frequency magnetic fields on ion channel and action potential in hippocampus CA3area of Kunming mouse neuronal ion channels and vertebral action potential.[Method]Prepare the Kunming mouse born in7to9days hippocampus CA3area pyramidal neurons by mechanical separation and enzyme digest. Voltage-clamp techniques were used to record the total whole-cell membrane currents, inward sodium current, delayed rectifier potassium current, analysis the curve of relationship of voltage and current, time and voltage, and activation or inactivation properties of control group and exposure group. The action potential characters were recorded by current-clamp techniques. The action potential threshold, resting potential, amplitude, and90%depolarization duration were measured.[Results]1. The single neurons prepared by acute isolated method had good spatial three-dimensional structure, smooth surface. There was complete dendritic or axons, in full compliance with the requirements of experiments.2. The electrophysiology characters of Kunming mouse pyramidal neurons(1) The whole-cell membrane total currents was obviously transmembrane voltage-dependent, both inward sodium current and outward current were contained.(2) The inward sodium current was time-dependent and voltage-dependent, the maximum current density of control group and exposure group (time:15min,30min,60min) were-294.46±7.46pA/pF,-234.41±3.21pA/pF,-223.37±5.32pA/pF, -194.88±2.35pA/pF (comparing with the control group, P<0.05). The half activation voltage of control group and exposure group were-30.22±0.46,-31.28±0.59(n=12, P>0.05), the slope factors were3.80±0.52,5.66±0.52(n=12, P<0.05), and the half inactivation voltage were-79.11±0.65,-68.94±0.54(n=12, P<0.05), the slope factors were12.59±0.58,8.60±0.48(n=12, p<0.05).(3) The delayed rectifier potassium current is time-dependent and voltage-dependent, maximum currents density were171.05±1.44pA/pF,153.04±0.45pA/pF,139.65±2.32pA/pF,100.91±1.53pA/pF (comparing with the control group, P<0.05). Recording the activation curve of control group and exposure group, it was shown that the half activation voltage were7,44±0.64,34.09±6.48(n=12, P<0.05), the slope factors were11.36±0.57,19.97±3.45(n=12, P<0.05).(4)After exposure with30minutes, the neurons resting membrane potential reduced from-64.54±1.35mV to-68.23±1.41mV (n=12, P<0.05); the action potential threshold changed from-48.44±1.34mV to-49.32±2.01mV (n=12, P>0.05), and the amplitude reduced from117.32±2.12m V to100.55±1.34mV (n=12, P<0.05), the action potential duration when reached90%delayed from14.63±0.34ms to21.74±1.47ms (n=12, P<0.05).[Conclusion]1. Power frequency magnetic fields of0.5mT reduced the excitability on hippocampus CA3area of Kunming mouse neuron in the sodium channel, from lowing the resting potential, and the activation process of the sodium channel, speeding inactivation and the amplitude of the action potential.2. Power frequency magnetic fields of0.5mT reduced the current of potassium channel, delayed the open time, slowed the speed of activation, and longed the time of depolarization. |
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