Effects of halothane on the transducer and potential activated currents of the crustacean stretch receptor.

Halothane was applied to the stretch receptor neuron of the crayfish (Astacus astacus) and the effects on the transducer properties and the potential activated currents were studied with potential clamp technique using two microelectrodes. Exposure to halothane reduced the frequency of action potentials during stretch. This was shown to be due to effects both on the action potential generating currents and the transducer current. Halothane partially blocked the TTX sensitive fast inward current in a dose-dependent manner (Apparent KD = 3 mM). Halothane also reduced the outward current produced by a positive potential step. Both the fast and the slow component were affected, although the fast outward current seemed to be most sensitive. There was little or no change in the currents resulting from negative potential steps. The peak of the receptor potential and the receptor current were very little affected by halothane. The amplitude of the static phase of the receptor potential was reduced to a greater degree than the static phase of the receptor current (cells treated with TTX). A change in reversal potential of about--13 mV was observed for the peak and the static phase of the receptor current in four cells indicating an increased cord conductance for the transducer channel.