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

Abstract

A study was made of the oxygen consumption of non-myelinated nerve fibers of rabbit desheathed cervical vagus nerves at rest and during activity. The average resting oxygen consumption (Qr) was 0.0924 [mu]mole/g. min at 21[degree] C. Stimulation for 1-3 min at 3/sec caused an extra oxygen consumption (Qs) of 816 p-mole/g. shock. When the frequency of stimulation was increased, to 10/sec and 30/sec, Qs fell. When the frequency was decreased, to 1/sec and 0.3/sec, Qs increased slightly. When the temperature was decreased, Qr fell; when the temperature was increased, Qs also increased. Temperature similarly affected Qs with high frequencies of stimulation, but had relatively little effect on Qs at low frequencies of stimulation. 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. When part of the sodium in the Locke solution was replaced by barium, Qr decreased (by 12%) whereas Qs increased (by 87%). Veratrine (1 [mu]g/ml.) increased both Qr (by 142%) and Qs (by 361%). Acetyl-choline (1.7 mM) increased Qr (by 32%). When nerves were transferred to potassium-free solutions there was little change in Qr, and Qs fell slightly (by 8%). When the potassium concentration in the Locke solution was increased 4-fold, Qr increased (by 27%). Salicylate (1-10 mM) increased Qr (by 24%) and abolished Qs. When the sodium of Locke solution was replaced by lithium, Qr decreased (by 19%) and Qs was abolished. In sodium-Locke solution ouabain (100 [mu][image]) decreased Qr (by 26%) and abolished Qs. In lithium-Locke solution ouabain also decreased Qr (by 28%). 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. The K/O2 ratio during pumping was about 5.0.