ASPHYXIAL DEPOLARISATION IN THE SPINAL CORD

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Abstract
Potential differences which develop between the gray matter and the anterior root during asphyxiation of the spinal cord were recorded. These potential changes are probably due to the depolarization first of the nerve cells, and later of the nerve fibers in the cord. After the arrest of respiration the gray matter starts to become negative after about 50 secs. After feeding N into the apparatus for artificial respiration the negativity began after about 20 secs. and after clamping the aorta after 8-9 secs. These differences are explained by the different speeds with which the spinal cord is deprived of oxygen. The negativity reaches a maximum in 2-4 mins. after which it usually slowly starts to regress. The negativity of the gray matter is probably due to the depolarization of the cells, the regression to the subsequent depolarization of the fibers in the cord. The negativity of the gray matter is quickly reversible when the cord is supplied with oxygen again. The recovery starts after about 20 secs. following a 1-2 mins. arrest of respiration or breathing of N. After 5 mins. of clamping of the aorta the recovery starts even quicker (avg. 9 secs.). After longer asphyxiations of the cord by clamping the aorta (10-70 mins.) the negativity of the gray matter also regresses after reoxygenation of the cord, though often not completely. In such expts. the regression is often preceded by a temporary increase of the negativity of the gray matter, which is believed to be due to the repolarization of the nerve fibers before the cells recover. After the longest asphyxiations (60-70 mins.) it was found that the cells in the spinal cord first repolarize, but a few hrs. later depolarize again. This is in accordance with previous observations which showed that the cells in the cord are destroyed a few hrs. after the end of such long asphyxiations. The relation between the state of polarization of the cells and the reflex activity is discussed.

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