The temperature dependence of the movement of sodium ions associated with nerve impulses

Abstract

SUMMARY1. The movement of sodium ions across the membrane of the squid giant axon was measured by the use of radioactive tracers. Unidirectional fluxes were measured at rest and when the nerve was stimulated. The difference was considered the extra flux association with nerve impulses.

The temperature dependence of the movement of potassium and chloride ions associated with nerve impulses.

“…The Q10 obtained in this study for extra potassium efflux is 1/1.5 + 0.1 which is not significantly different than the Q10 for extra sodium influx found by Cohen & Landowne (1974) of 1/1-2 to 1/1.6. Thus, it appears as if both ion movements have low temperature dependence and there is no need to postulate the movement of some other ion at low temperatures to compensate for an imbalance of these two ions.…”

“…Influx and efflux of 42K and 36Cl were measured in intact squid giant axons using standard techniques (Landowne, 1975;Cohen & Landowne, 1974;Hodgkin & Keynes, 1957;Caldwell & Keynes, 1960). A standard artificial sea water was used with the following concentration of ions (in mM): Na+, 460; K+, 10; Ca2+, 10; Mg2+, 55; C1-, 600; HEPES (N-2-hydroxyethyl piperazine N'-2-ethanesulphonate) buffer pH 7-4, 2.…”

“…This was found to be the case in Sepia axons in experiments using radioactive tracers (Keynes, 1951) and is consistent with the predictions made by Hodgkin & Huxley (1952b) on the basis of their electrical measurements. Recently, Cohen & Landowne (1974) measured the extra influx of sodium associated with nerve impulses at different temperatures and found a lower temperature dependence than had been predicted by Hodgkin & Huxley (1952b). The measured sodium fluxes had a Q10 of 1/1.2-1/1.6 whereas the predictions lead to a Q10 of 1/3-1/3.6.…”

“…In 1954, Shanes measured the temperature dependence of the net potassium efflux in squid and crab nerves and reported qualitative conformation with the hypothesis of Hodgkin & Huxley (1952b). At first glance, this would seem to be in conflict with the findings of Cohen & Landowne (1974). However, Shanes (1954) used massive stimulation and measured relatively small differences in the potassium concentration of the sea water bathing the nerves.…”

Levels of high‐energy phosphates in crayfish nerve during prolonged repetitive impulse activity.

“…(3) Low temperatures may also inhibit metabolic activity (cf. Cohen & Landowne, 1974), leading to an increased utilization of ArgP.…”