Influence of short-term ischemia on segmental spinal cord reflex functions in cats

In the lumbar spinal cord in cats, microcirculatory (laser Doppler flowmetry) and segmental neurophysiological parameters [monosynaptic reflexes of a flexor and extensor, polysynaptic reflexes from a cutaneous nerve, and the cord dorsum potential (CDP)] were determined in context with ischemias of 1-10 min. Ischemias were achieved by aortic snare occlusion of the descending aorta and were pooled into deep and moderate ones (0-20% and 20-50% residual spinal cord blood flow). Three phases of reaction to ischemia were defined: a period of decreasing responses, a period of delay until recovery, and a recovery period from beginning to completeness of recovery. Although the period of decreasing responses was relatively constant, the delay until recovery could be correlated with duration and depth of ischemia. The recovery period depended mainly on the duration of ischemia. For 2-6-min ischemias, the correlation between depth and duration of ischemia to the delay until recovery or to the recovery period tended to be linear. The period of decreasing responses, the delay until recovery, and the recovery period of mono- and polysynaptic reflexes behaved in a comparable way and demonstrated similar susceptibility to ischemia. The CDP turned out to be the most stable response, indicating a higher resistance of the first-order interneurons to ischemia than of motor neurons.