Changes in spinal evoked potentials following local cooling of the spinal cord in the cat

Potentials evoked by stimulation of the ulnar nerve and the thoracic cord were recorded in the cervical cord of Nembutalized, curarized cats. The sites of the spinal cord stimulated or recorded therefrom were cooled, all together or independently, in 30 cats, and the effects of the cooling on the evoked potentials were investigated. In all cases, the peak latency tended to increase. On the other hand, the amplitude gradually decreased in the cats in which the stimulation site was cooled, gradually increased in the cats in which the recording site was cooled, and transiently increased when the whole area extending from the stimulation site to the recording site was cooled. In 20 cats, the effects of cooling on the anoxic spinal cord were studied. In the hypothermic cats, the evoked potentials disappeared in 24 min, and in the normothermic cats in 13 min. The difference was statistically significant (p less than 0.01). This indicates that cooling could counteract the effects of anoxia to a certain extent.