THE RELATION BETWEEN THE AFTER-POTENTIAL AND OXIDATIVE PROCESSES IN MEDULLATED NERVE

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Abstract
The effect of veratrin upon the metabolism of the sciatic nerve of the frog, Rana pipiens, was studied during rest and activity. The O2 consumption of resting veratrinized nerves was about 15% greater than that of unpoisoned paired nerves kept as a control. The O2 consumption of single nerves was measured in a sensitive volumeter when the nerves were stimulated with shocks just strong enough to give maximal A spikes, the nerve responses being at all times controlled by observations of the spike and after-potentials with an oscillograph. Normal nerves showed no definite increase in O2 utilization when stimulated twice per sec., but veratrinized nerves under the same conditions showed an increase of 5-15% above the resting rate. The responses of the veratrinized nerves were characterized by very large after-potentials. CO2 depresses the after-potential in nerve more rapidly than it does the spike. Illumination causes the after-potential to rise very much more rapidly than the spike, but this rise is temporary and, after exceeding the normal value, the after-potential may recede considerably below the initial level even during illumination. It is concluded that the passage of a spike along a nerve initiates a burst of oxidation which must be associated with the processes of the after-potential. This oxidation is mediated by a hemin-like catalytic system which can be poisoned by CO2 and which is at least partially photosensitive.

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