Rat Trigeminal Evoked Potential Studies

Objective:To investigate recording methods and characteristics of trigeminal evoked potential(TEP), observe changes of TEP to anoxia, provide normative data for further studies to various pathologic state.Methods:Under anesthesia, the Sprague-Dawley rats were fixed on the stereotactic instrument, with two stimulus electrodes inserted into the subcutaneous layer of the root of the second,third whiskers in the third row,and given single square stimulation with wavelength 0.1ms. TEPs were recorded on the contralateral epidural surface. The recording time was 120ms, wave filter 1000Hz ~3000Hz, gain 10,000 times, and summation 5~10times.The basic waveform and the best recording point were determined by recording each time when recording electrode was removed1mm, and the best stimulation of voltage were determined by increasing voltage from 0v to 10.0v,then the typical normal TEPs were recorded. Changes of TEP to various anoxia stage were recorded on the simplified models of cerebral anoxia made by clipping trachea.Results: Waveforms of TEP were most apparent, amplitudes and latencies were most stable on the point of 2~3mm posterior from bregma and 5~6mm lateral from midline. The basic waveform was N1-P-N2 type. TEPs could be recorded from0.2~0.5v stimulation, amplitudes were increased with increase of voltage stimulation, waveforms and amplitudes were stabilized with intensity of stimulation arriving at 3.0~4.0v. The normal TEP in rat N1L 8.75±0.49ms,N1A0.93±0.27μv,PL147.36±0.42ms,PA0.64±0.25μv,N2L28.78±0.61ms,N2A0.25±0.09μv. The results of TEP under various anoxia stage compared to normal. There was significant difference in amplitudes of wave N1,P,N2 between normal and the trachea clipped, P<0.05 or P<0.01, and a tendency of decrease with clipping time prolonged; there was significant difference in the latencies of wave N1,N2 between normal and the clipped 9min, P<0.05, no significant difference between normal and others, P>0.05, and a tendency of increase in the latencies wave N1 with the clipping time prolonged, no significant difference in the latencies of wave P between normal and the trachea clipped.Conclusion:TEPs could be recorded ParⅠ area of somatosensory cortex in rat. The best recording point is on the point of 2~3mm posterior from bregma and 5~6mm lateral from midline. The best intensity of voltage stimulation is 3.0~4.0v. The basic waveform is N1-P-N2 type. Amplitudes of wave N1,P,N2 are sensitive to anoxia, the latencies of waveN1,N2 have response to anoxia, but wave P not.