Study On The Antiepileptic Effect And Mechanism Of Low-Intensity Pulsed Ultrasound Vagus Nerve Stimulation

BACKGROUND:Epilepsy is a very common chronic nervous system disease.In recent years,the classical neuromodulation methods represented by vagus nerve stimulation(VNS)have been gradually applied to the treatment of drug-resistant epilepsy,which has confirmed its efficacy and safety.At the same time,non-invasive neuromodulation methods like low-intensity pulsed ultrasound(LIPUS)has sprung up.Transcranial non-invasive ultrasound stimulation can treat various central diseases,and ultrasound can also be used to stimulate peripheral nerves.OBJECTS:Combine safe and effective vagus nerve stimulation with non-invasive,accurate and convenient ultrasonic neuromodulation concept to form a highly innovative low-intensity pulsed ultrasound vagus nerve stimulation(LIPUS-VNS)method for the treatment of epilepsy.To study the feasibility,efficacy,optimal parameters and antiepileptic mechanism of its application in rat epilepsy model.METHODS:The first stage is to establish an acute rat epilepsy model suitable for ultrasonic stimulation pattern by combining a variety of anesthesia drugs and a variety of epileptogenic drugs and comparing the seizure characteristics of rats.The EEG monitoring system is tested and the evaluation method is also established.Test and calibrate ultrasonic transducers and supporting signal generators,power amplifiers and other equipment.The above ultrasound equipment,EEG devices and animals were integrated into the experimental platform of ultrasound VNS.In the second stage,the ultrasound VNS experimental platform was used to implement LIPUS-VNS in epileptic rats with 3 pulse repetition parameters,2 stimulation intensity parameters and 2 stimulation time window schemes respectively.Count the number of major seizures and the total duration of major seizures on the EEG monitoring devices,so as to judge the curative effect of LIPUS-VNS on epilepsy,and summarize the best stimulation parameters.The third stage is to design the LIPUS-VNS comparing experiment of vagotomy rats,the LIPUS-VNS comparing experiment of healthy rats,observe the activation of central nuclei in epileptic rats after LIPUS-VNS treatment,and explore the antiepileptic mechanism of LIPUS-VNS in 3 aspects:the initiation,transmission and antiepileptic terminal effect of ultrasonic mechanical signal.RESULTS:In the first stage,after comparison,the acute epilepsy model of rats was made by intraperitoneal injection of 60 mg/kg ketamine anesthesia and intraperitoneal injection of 100 mg/kg pentylenetetrazole.The focus of the ultrasonic transducer was measured to be 5 cm away from the outlet after calibration.Combined with a collimator with a height of 3.5 cm,the transducer can accurately stimulate the cervical segment of the vagus nerve in rats.The experimental platform of ultrasound VNS runs well and can support follow-up research.In the second stage,after rats be treated by LIPUS-VNS,the number of seizures decreased,the seizure time shortened and the seizure interval prolonged.It is considered that LIPUS-VNS has a good antiepileptic effect.When the pulse repetition rate is 20 Hz and the stimulation intensity is 1050mv,the treatment effect is optimized.Moreover,LIPUS-VNS has antiepileptic effect both in the early intervention of epilepsy and the treatment after the onset of epilepsy.Among them,it has a more significant therapeutic effect on the treatment stage.The third stage revealed that LIPUS-VNS had no antiepileptic effect in the absence of vagus nerve.LIPUS-VNS on healthy rats showed the activation of locus coeruleus and amygdala in the brain.After examining the activation of neurons among the central nuclei of epileptic rats treated by LIPUS-VNS,it was found that the abnormal excitability in the hippocampus was significantly reversed by LIPUS-VNS,which benefited other nuclei in the center by reducing their abnormal excitability.CONCLUSION:①The existing technology can realize non-invasive and accurate ultrasonic vagus nerve stimulation on small animals.②LIPUS-VNS has antiepileptic effect in both the early intervention and post onset treatment of epilepsy.③LIPUS stimulation of the vagus nerve at a repetition rate of 20 Hz for 15 minutes has a good enough antiepileptic effect.Increasing the intensity within a certain range will enhance the therapeutic effect.④The central circuit mechanism of LIPUS-VNS depends on the related nuclei such as locus coeruleus and amygdala.⑤ The antiepileptic mechanism of LIPUS-VNS is related to the reduction of abnormal excitability of epileptic hippocampus.