Acute effects of x‐radiation on reflex arcs of the spinal cord

Abstract

In cats, 5,000 r of 250-kv. X-ray were given to the exposed lumbar spinal cords. Some animals were observed for clinical effect, and some were studied for electrophysiologic changes in spinal cord reflexes. Some early weakness was observed but completely disappeared in twenty-four hours. Complete paraplegia developed on the sixth or seventh day. Anterior root responses to posterior root stimulation before and immediately after irradiation were investigated. By the fifth hour after irradiation, response time became significantly delayed, indicating a slowed conduction rate. The total length of time of the response was not significantly changed until nine to ten hours after irradiation. The polysynaptic response gradually diminished in amplitude, and, eleven hours after irradiation, was almost absent. At this time, the monosynaptic spike showed marked reduction in amplitude but was never more than a single spike. This later suggested cellular of synaptic alterations. The effect of pentobarbital on the cat electroencephalogram was investigated; 6 fairly distinct electroencephalographic patterns were found associated with increasing depth of anesthesia. As the cat goes into lower levels of anesthesia, the anterior root response with posterior root stimulation is significantly altered; pentobarbital should not be used when this response is being studied.