The Impact Of High Intensity Ultrasound On The Rabbit Sciatic Nerve

Objective: To determine the changes of the action potential peak value and maximal nerve conductive velocity of the rabbit sciatic nerves after the exposure of high intensity ultrasound(HIU) (7.1MHz,45.86W/cm2)and to establish the experimental base for treating refractory pain with HIU. Methods: The rabbit sciatic nerves were exposed to high intensity ultrasound of different doses; The rabbit sciatic nerve electrophysiologic parameters, such as maximal nerve conductive velocity(NCV),action potential peak value and the latency of action potential ,were measured before and after the exposure. The corresponding histologic and ultrastructure changes of the nerve exposed were observed.Results:The larger dose of the HIU , the greater decrease of the action potential peak value .After 15 second exposure of HIU,the decreases of action potential peak value were:9.0 percent on tibial nerve,40.3 percent on sural cutaneous nerve; After 20 secondexposure:18.1 percent on tibial nerve,46.0 percent on sural cutaneous nerve; After 25 second exposure:41.0 percent on tibial nerve,67.1 percent on sural cutaneous nerve; After 35 second exposure:81.1 percent on tibial nerve,87.0 percent on sural cutaneous nerve ,6 sciatic nerves were blocked completely in group 35s.The decreases of maximal nerve conductive velocity were 77.5 percent on tibial nerve, 66.8 percent on sural cutaneous nerve after 35 second exposure of HIU;while there were no significant changes of maximal nerve conductive velocity after 15s,20s, 25s exposure of HIU on both nerves.Slight deformation of the myelin sheath was observed at the dose of 45.86W/cm2 ×15 seconds electron microscopically and myelin sheath loss and breakdown and axon degeneration were observed at the dose of 45.86W/cm2×35seconds both light and electron microscopically. Conclusions: the larger dose of HIU ,the higher degree of the injury of the sciatic nerve; At the same dose,the sural cutaneous nerve is easier to be injured than the tibial nerve. sciatic nerve may be blocked with HIU partially or completely.