The effect of temperature on the nerve-blocking action of benzyl alcohol on the squid giant axon.

The action of benzyl alcohol was studied on the voltage-clamped giant axons of Loligo forbesi. The depressant effect of 7.5 mM-benzyl alcohol on the action potential amplitude and peak rate of rise was more marked at a low (8 degrees C) than at a high temperature (16.5 degrees C). A small depolarization (approximately 5 mV) was also produced. These effects were usually reversible. Benzyl alcohol (7.5 mM) selectively depressed the amplitude of the peak early current. The maximum inward current was depressed to 0.65 and 0.67 of the control value at 20 degrees C and 7 degrees C respectively. This effect was usually reversible. Benzyl alcohol also depressed the peak inward conductance (gNa but had no effect on the time to peak early current. A small reversible decrease in the time constant of inactivation (tau h) was caused by benzyl alcohol (7.5 mM). This was usually reversible on washout of the anaesthetic. Benzyl alcohol (7.5 mM) had no effect on the time course of activation or the amplitude of the delayed outward current. The curve of the steady-state inactivation parameter (h infinity) for the Na current against the conditioning membrane potential was shifted by benzyl alcohol in a hyperpolarizing direction (at h infinity = 0.5 the shift was an average of 3.3 mV and was reversible). Increasing the temperature from 7 to 20 degrees C shifted the curve in a depolarizing direction by approximately 10 mV. The reason for the increased nerve-blocking action of benzyl alcohol at the lower temperature is discussed.