The oxygen consumption of mammalian non-myelinated nerve fibres at rest and during activity

Abstract

1. A study has been made of the oxygen consumption of non-myelinated nerve fibres of rabbit desheathed cervical vagus nerves at rest and during activity.2. The average resting oxygen consumption (Q(r)) was 0.0924 mumole/g. min at 21 degrees C. Stimulation for 1-3 min at 3/sec caused an extra oxygen consumption (Q(s)) of 816 p-mole/g.shock.3. When the frequency of stimulation was increased, to 10/sec and 30/sec, Q(s) fell. When the frequency was decreased, to 1/sec and 0.3/sec, Q(s) increased slightly.4. When the temperature was decreased, Q(r) fell; when the temperature was increased, Q(s) also increased. Temperature similarly affected Q(s) with high frequencies of stimulation, but had relatively little effect on Q(s) at low frequencies of stimulation.5. An isolated single shock seemed to produce an increase in oxygen consumption of about 1200 p-mole/g, and this value was largely independent of temperature.6. When part of the sodium in the Locke solution was replaced by barium, Q(r) decreased (by 12%) whereas Q(s) increased (by 87%).7. Veratrine (1 mug/ml.) increased both Q(r) (by 142%) and Q(s) (by 361%).8. Acetylcholine (1.7 mM) increased Q(r) (by 32%).9. When nerves were transferred to potassium-free solutions there was little change in Q(r), and Q(s) fell slightly (by 8%).10. When the potassium concentration in the Locke solution was increased 4-fold, Q(r) increased (by 27%).11. Salicylate (1-10 mM) increased Q(r) (by 24%) and abolished Q(s).12. When the sodium of Locke solution was replaced by lithium, Q(r) decreased (by 19%) and Q(s) was abolished.13. In sodium-Locke solution ouabain (100 muM) decreased Q(r) (by 26%) and abolished Q(s). In lithium-Locke solution ouabain also decreased Q(r) (by 28%).14. All or nearly all of the oxygen consumed at rest or during activity seemed to be used to pump potassium ions into, and sodium ions out of, the axoplasm.15. The K/O(2) ratio during pumping was about 5.0.