Some effects of n‐pentane on the sodium and potassium currents of the squid giant axon.

Abstract

Na and K currents were recorded in intracellularly perfused squid [Coligo forbesi] grant axons before, during and after exposure to solutions of n-pentane in artificial sea water. The currents were fitted with equations similar to those proposed by Hodgkin and Huxley (1952), and the changes in the parameters of these equation n the presence of pentane were calculated. In the range of membrane potential -40 to 40 mV, the time constants for activation (.tau.m) and inactivation (.tau.h) of the Na current, and for activation (.tau.n) of the K current were all reduced by the pentane. The curve of the steady-state inactivation parameter (h.infin.) for the Na current against membrane potential was shifted by the pentane in a hyperpolarizing direction (at h.infin. = 0.5 this shift was .apprx. -15 mV in 275 .mu.M-pentane) and the slope at all potentials was reduced. The curve of the steady-state activation parameter (m.infin.) for the Na current against membrane potential also was shifted by the pentane in a hyperpolarizing direction (in 153 .mu.M-pentane, 10 mV at m.infin. = 0.5). The maximum Na and K conductances .hivin.gNa and .hivin.gK were lowered by the pentane, though not usually completely reversibly. The changes in position and slope fo the steady-state inactivation curve have been tentatively accounted for in terms of an increase in membrane thickness.