Orexin a elicits arousal electroencephalography without sympathetic cardiovascular activation in isoflurane-anesthetized rats.

UNLABELLED: We studied the effects of intracerebroventricular injection of the novel neuropeptide orexin A on electroencephalogram (EEG) and autonomic nervous system activity in rats under isoflurane anesthesia. The administration of orexin A changed burst suppression patterns to arousal patterns on the EEG at 1.0 minimum alveolar anesthetic concentration (MAC) isoflurane and decreased the burst suppression ratio at 1.5 MAC isoflurane. However, orexin A did not influence the heart rate or mean arterial blood pressure at either isoflurane concentration. These findings demonstrated that orexin A elicited anesthetic arousal under isoflurane anesthesia in terms of EEG pattern without sympathetic cardiovascular activation in the rat. IMPLICATIONS: The novel neuropeptides orexins induce arousal associated with activation of the sympathetic nervous system in conscious rats. It is not known whether orexins affect the electroencephalogram (EEG), autonomic nerve activity, or both under anesthesia. Orexin A induced EEG arousal without sympathetic cardiovascular activation in the isoflurane-anesthetized rat. Orexin A might influence the depth of anesthesia.