EFFECTS OF PYRUVATE ON NERVOUS ACTIVITIES
1954 Volume 4 Pages 42-51
Details
1954 Volume 4 Pages 42-51
Nervous activities (energy required for it), such for instance as the maintenance of the threshold or the accumulation of potassium in nerve fiber, are closely concerned with the oxydative metabolism going on in the tissue.
The experiments performed substantiated this relation and, the results obtained were as follows:
1) Threshold and resting potential. A 10-20mM pyruvate-Ringer solution applied to one side of a Ranvier node brought about an approximately 30% average drop in the threshold in the node, which, after being maintained at that level for half an hour or so, was raised to a level slightly higher than the original in 15 minutes. Futher application of pyruvate brought it down again. On the opposite side of the Ranvier node, the threshold fell 10-15% and rose to the original level afterwards through the same process as in the proceeding case. The effect of pyruvate was inhibited by the application of 2-4 dinitrophenol or by the use of a material which was dissected several hours before experiment. The resting potential of a node affected by pyruvate rose about 15mV with the fall of the threshold and then passing through about the same process as the threshold, fell back to the original level.
2) Oxygen consumption. The oxygen consumed was increased by 1.13mM O 2-about 7.2×10-3 M ATP per gram of fresh nerve fiber per 30 minutes-in nealry the same period of time as was required for the changes in the threshold and resting potential by addition of pyruvate (15mM). The amount of ATP required a 10% drop in the threshold is about 0.4×10-3M ATP per g. per minute.
3) Reaction of nerve fiber to 0.11 M NaCl solution and action of pyruvate. The threshold of a nerve fiber was lowered by potassium ions in a low concentration (2.7mM or less). It was lowered in 0.11 M NaCl solution under some conditions too. However by introduction of pyruvate the threshold is not affected by application of 0.11 M NaCl solution. This will lead us to conclude that some potassium ions that leaked out from the inner-side of the Ranvier node, when 0.11 M NaCl solution is introduced at this node, caused the threshold decrease.
4) Effect of pyruvate on potassium in nerve fiber. Pyruvate has a tendency give rise to a decrease in the potassium leakage.
