Effects of sevoflurane and halothane on the hypothalamic noradrenaline release in rat brain

Abstract

Previous studies suggest that the posterior hypothalamus is closely related to arousal from volatile anaesthetics. This study was designed to investigate the release of noradrenaline from the posterior hypothalamus during emergence from sevoflurance anaesthesia, compared with halothane anaesthesia. Earlier clinical researches have shown more rapid emergence after sevoflurane than after halothane, when they are used in equivalent concentrations. Twenty four Wistar rats were used. A microdialysis probe was inserted in the posterior hypothalamus, using the diagram of paxinos, in each rat 24 h before general anaesthesia. Twenty minute period samples of 60 μL dialysate were collected into a high performance liquid chromatograph with electrochemical detector. The remaining ten rats were used to determine blood gas analysis during sevoflurane (five rats) and halothane (five rats) anaesthesia. Seven rats received 2.6% sevoflurane in air for 1 h and seven rats receive 1.0% halothane in air for the same drug in the microdialysis system. Noradrenaline released from the posterior hypothalamus as significantly increased in both groups of rats during the emergence from the anaesthesia. The magnitude of the increase was similar in both groups, however, a longer response was observed in the halothane group than in the sevoflurane group. No significant differences between anaesthetic groups were detected by blood gas analysis. We have found that the increased noradrenaline release persisted for longer following halothane anaesthesia than following sevoflurane anaesthesia indicating that the recovery time is shorter after sevoflurane anaesthsia than after halothane anaesthesia. These findings are consistent with clinical experience using these agents.