| Transcranial ultrasonic-magnetic stimulation is a new non-invasive neuromodulation method with deep stimulation depth and good focus,which is of great significance for the study of its potential biological effects.In view of the key role of neuronal discharge and ion channel activity in neuroregulation,the purpose of this study was to explore the effects of ultrasonic-magnetic stimulation on neuronal discharge and potassium channel current,and to reveal the mechanism of neuronal regulation.In this paper,the theoretical basis of transcranial magnetic stimulation is studied,and the effects produced by it are analyzed.The distribution of sound field and the distribution of induced electric field are calculated.The spontaneous action potential,transient outward potassium current and delayed rectifier potassium current of hippocampal CA1 neurons in fresh brain of SD rats were recorded by patch clamp technique.Furthermore,based on the Izhikevich neuron model,the action potentials of conventional and fast discharges of neurons under transcranial magnetic stimulation were modeled and simulated.The details are as follows:In this paper,whole-cell patch clamp technique was used to record the changes of electrophysiological properties of pyramidal neurons in hippocampus of rats after different stimulation.In order to investigate the effects of ultrasonic-magnetic stimulation on neuronal excitability,the experiment collected the spontaneous action potential of neurons.Through the statistics and comparison of the spontaneous discharge frequency,it is found that the ultrasonic-magnetic stimulation can significantly increase the discharge frequency and amplitude of the action potential.The results show that ultrasonic-magnetic stimulation can increase the excitability of pyramidal neurons in the CA1 region.The transient outward potassium current and delayed rectifier potassium current of the neurons were further collected,and the I-V curve and kinetic curve were drawn,and the kinetic characteristics were analyzed.The results show that compared with the control group,ultrasonic-magnetic significantly reduces the amplitude of the instantaneous outward potassium current,and makes the steady-state activation curve move towards depolarization and the inactivation curve move towards negative voltage,which makes the channel more difficult to activate,easier to inactivate and takes longer to recover after inactivation.On the other hand,ultrasonic-magnetic also reduces the amplitude of the delayed rectifier potassium current,and makes the steady-state activation curve of the delayed rectifier potassium current move to the left,making the delayed rectifier potassium channel more easily activated.These results suggest that ultrasonic-magnetic stimulation increases the excitability of neurons,which may be caused by the inhibition of ultrasonic-magnetic stimulation on instantaneous outward potassium current and delayed rectifier potassium current.In this paper,an improved neuron model is also established based on the Izhikevich model.The discharge activity of conventional discharge neurons and fast-discharge neurons under transcranial magnetic stimulation is simulated.Based on the improved model,the discharge behavior of neurons under the ultrasonic-magnetic effect and mechanical electrical effect was studied.The simulation results show that different transcranial magnetic stimulation parameters determine the difference in induced current density,resulting in different discharge activities.The results further emphasize that both the mechanical electrical effect and the ultrasonic magnetic effect have a non-negligible role in the regulation of neural excitability.In summary,the promotion of neuronal excitability by transcranial magnetic stimulation may be due to its inhibition of transient outward potassium current and delayed rectifier potassium current,which are critical to the action potential repolarization.This paper studies the effects of biophysical effects of transcranial magnetic stimulation on neurons.These results have important reference value for clarifying new physical cell effects in the future,which will help to further explore new methods of acoustic magnetic nerve control. |
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