Inhibition by halothane of potassium‐stimulated acetylcholine release from rat cortical slices

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Abstract
1 Cholinergic neurones in the basal forebrain are linked to cortical activation and arousal. 2 The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) would significantly reduce depolarization-evoked acetylcholine (ACh) release from rat cortical slices. 3 ACh release was measured from rat cortical slices by a chemiluminescent technique. 4 Depolarization-evoked ACh release was inhibited significantly by halothane with an IC50 of 0.38%. This value equates to 0.3 MAC (the minimum alveolar concentration at which no movement occurs to a standard surgical stimulus in 50% of subjects) for the rat. 5 The potent effect of halothane on ACh release suggests that this mechanism may be a target for the action of volatile anaesthetic agents. This in vitro effect on ACh release is consistent with effects of halothane reported in vivo.