Barbiturates increase the rate of voltage‐dependent inactivation of the calcium current in snail neurones

Abstract

Effects of barbiturates (thiopentone, pentobarbitone, phenobarbitone and barbitone) on the calcium current (ICa) in identified Helix neurones were studied, using a conventional suction pipette technique. Barbiturates depressed the maximal peak amplitudes (MPA) of ICa in a dose‐dependent manner without shifting the current‐voltage relationships along the voltage axis. Barbiturates accelerated the decay phase of ICa at high concentrations (1 × 10−4 to 3 × 10−3 m), at which concentrations double‐pulse experiments showed the increased rate of a voltage‐dependent inactivation of ICa. It is concluded that the acceleration of the decay phase of ICa by barbiturates may be due to the increased rate of the voltage‐dependent inactivation of ICa. 1983 British Pharmacological Society