OBJECTIVE: To evaluate changes of the spinal cord conductivity by investigating the cortical somatosensory evoked potentials (SEPs) after angular rotations of the cervical spine in the rats. METHOD: Ten rats (Sprague-Dawley, 300~350 gm) were used. The trunk and head were fixed in the instrument for measuring rotational angles of the cervical spine. P1 latencies and P1-N1 amplitudes of the SEPs were obtained by stimulation of the posterior tibial nerve at the left hind paw. Thin scalp needle electrodes were placed subcutaneously at the 3 mm posterior to the vertex and nasion. We measured the parameters of the potentials at each 10o angular loading and compared the values measured immediately with those 5 minutes after each rotation. RESULTS: P1 latencies were 19.9+/-5.5 msec at rest, 20.1+/-5.8 msec at 90 degrees, 20.5+/-5.8 msec at 100 degrees, 21.2+/-6.2 msec at 120 degrees and 21.7+/-6.1 msec at 130 degrees, which were significantly prolonged above 100 degrees rotational loadings (p<0.05). The potentials disappeared at 140~170 degrees in some rats. The P1 latencies were prolonged according to increasing of the head rotational angles, however, P1-N1 amplitudes were not significantly decreased until absence of the potentials. There was no significant difference of the P1 latencies and P1-N1 amplitudes between potentials recorded immediately after rotational loading and at 5 minutes after rotation. CONCLUSION: P1 latencies of the SEPs according to the head rotation were significantly prolonged over 100 degrees loadings in the rats. This result suggested possible impairment of the spinal cord conductivity over 100 degrees rotational loading of the cervical spine in the rat.