Oxygen consumption and phosphate efflux in mammalian non‐myelinated nerve fibres.

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Abstract
A comparison was made between the labeled phosphate efflux from the non-myelinated fibers of the desheathed rabbit vagus nerve at 37.degree. C and the corresponding O2 consumption at rest, during activity and during a variety of experimental interventions. The resting rate constant of phosphate efflux was 2.61 .times. 10-3 min-1; electrical stimulation (10-1, 3 min) produced an extra fractional loss of 6.75 .times. 10-6 impulse-1. The corresponding resting O2 consumption was 0.484 mmol/kg-1 min-1; the extra O2 consumption with electrical activity was 0.467 .mu.mol/kg-l impulse-1. Ouabain (100 .mu.M) produced a sustained depression (of about 40%) of the resting O2 consumption, accompanied by a transient fall (of about 14%) in the rate constant of phosphate efflux. Na salicylate (10 mM) or Na arsenate (1 mM) produced a much larger increase in phosphate efflux than in resting O2 consumption. Changing the external phosphate concentration (between 0.02 and 2 mM), addition of acetylcholine (1.7 mM) and addition of lanthanum (20 .mu.M).sbd.all of which markedly affect the phosphate efflux in rabbit non-myelinated fibers.sbd.had little or no effect on the resting O2 consumption or on the extra O2 consumption with electrical stimulation. Changing the external Ca concentration (between 0.09 and 9 mM) had minor effects on the O2 consumption (resting and stimulated) and on the rate constant of resting phosphate efflux. Although changes in nerve metabolism produce changes in the phosphate efflux expected on the basis of the concomitant changes in the internal concentration of Pi, the coverse is not true; increases and decreases in the phosphate efflux rate constant do not necessarily signal corresponding metabolic changes.