Effects of halothane and hydrostatic pressure on sodium channels in squid axon

The effects of halothane and hydrostatic compression have been studied on the voltage-dependent sodium conductances in the squid giant axon. Compression to 150 atmospheres reduced the time course of both the activation and inactivation phases of the sodium current, reduced the amplitude of the peak inward current, and shifted the sodium reversal potential in a slightly hyperpolarizing direction. Halothane also depressed the sodium current amplitude and shifted the reversal potential but did not alter the membrane kinetics. Subsequent compression to 100 ATA did not restore the inward current flux to its control value, nor reverse the shift in the sodium reversal potential. We conclude that pressure and halothane do not act antagonistically at common sites in this preparation.