British journal of anaesthesia
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Gamma (30-80 Hz) and high-gamma (80-200 Hz) thalamocortical EEG rhythms are involved in conscious processes and are attenuated by isoflurane and propofol. To explore the hypothesis that this attenuation is a correlate of anaesthetic action, we characterized the effect dexmedetomidine, a selective adrenergic α-2 agonist with lesser hypnotic potency, on these rhythms. ⋯ Dexmedetomidine attenuates high-frequency thalamocortical rhythms, but to a lesser degree than isoflurane and propofol. The main differences between dexmedetomidine and the other anaesthetics involved thalamic rhythms, further substantiating the link between impaired thalamic function and anaesthesia. Increased delta coherence likely reflects cyclic hyperpolarization of thalamocortical networks and may be a marker for loss of consciousness.
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Isoflurane preconditioning (IPC) induces cerebral ischaemic tolerance, but the mechanism remains poorly understood. The aim of this study was to determine changes in mitochondrial function in the brain after IPC, and whether the cannabinoid receptor 1 (CB1R) could be involved in the mechanism of mitochondrial protection mediated by IPC. ⋯ Our results indicate that IPC elicits brain ischaemic tolerance and mitochondrial protection by activating the CB1R, which provides a new mechanism for IPC-induced neuroprotection against cerebral ischaemia.