RESUMO
PURPOSE: Electrophysiologically assess conduction pathways of the pyramidal and extrapyramidal systems in rats and predict the pathways involved in spinal cord injuries. METHOD: The motor area of the cerebral cortex, medullary reticular nucleus, lateral vestibular nucleus, and red nucleus of adult Sprague-Dawley rats were stimulated with microelectrodes. Laminectomies were performed at the C6, T10 and L2 cord level. Field potentials evoked by stimulation of the cerebral cortex and the three motor nuclei were recorded with a glass microelectrode of 1.5~2.5 Mohm filled with 0.2M NaCl. To construct a cross-sectional map of field potentials, recording was made in 7 tracks equally spaced across the spinal cord. In each track, field potentials were recorded at seven equally spaced points from the ventral to dorsal cord. RESULT: Stimulation of the cerebral motor cortex evoked 5 wanes, such as P1, P2, P3, P4, P5. P1 was monitored mainly in the bilateral dorsal half of the spinal cord and other wades mainly in the ventral half of the spinal cord. With lateral vestibular nucleus stimulation, 1 or 2 short duration biphasic waves followed by a longer duration positive wave were monitored mainly in the ipsilateral ventrolateral funiculus of the cord. Field potentials produced by stimulating the medullary reticular nucleus were shown mainly in the ventromedial funiculus, and their latencies were longer than those from the vestibular nucleus stimulation. Field potentials generated by the stimulation of the red nucleus were monitored mainly in the dorsolateral funiculus. CONCLUSION: motor evoked potential is clinically useful to evaluate the descending pathways of the spinal cord.