K+ concentration influences methohexitone inhibition of K(+)-stimulated release of [3H]noradrenaline from minislices of rat cerebral cortex

Abstract

This study investigated the effect of methohexitone, a barbiturate anaesthetic, with variation of the K+ concentration used to stimulate [3H]noradrenaline release from superfused minislices of rat cerebral cortex. The amount of [3H]noradrenaline released by K(+)-stimulation depended on the concentration of K+ used (increasing release was seen at 10-50 mM K+). Methohexitone (10(-7)-3 x 10(-4) M) added to the superfusing medium did not alter the basal efflux of [3H]noradrenaline, but high concentrations inhibited K(+)-stimulated release. Using 12.5 mM K+, inhibition of release was observed only at 10(-4) M methohexitone (48% inhibition); the effect of 25 mM K+ was reduced by 3 x 10(-5) M (72% inhibition) and higher concentrations while release stimulated by 50 mM K+ was inhibited by 10(-5) M methohexitone (30% inhibition) and higher concentrations.