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Aim:To investigate the effects of orexin A on release of histamine,norepinephrine,and serotonin in the frontal cortex of mice.Methods:Samples for measuringhistamine,norepinephrine,and serotonin contents were collected by in vivomicrodialysis of the frontal cortex of anesthetized mice.The histamine,noradrenaline,and serotonin content in dialysates were measured by HPLCtechniques.Results:Intracrebroventricular injection of orexin A at doses of 12.5,50,and 200 pmol per mouse promoted histamine release from the frontal cortex ina dose-dependent manner.At the highest dose given,200 pmol,orexin A signifi-cantly induced histamine release,with the maximal magnitude being 230% overthe mean basal release.The enhanced histamine release was sustained for 140min,and then gradually returned to the basal level.However,no change in nore-pinephrine or serotonin release was observed under application of the same doseof orexin A.Conclusion:These results suggest that the arousal effect of orexin Ais mainly mediated by histamine,not by norepinephrine or serotonin.
Aim: To investigate the effects of orexin A on release of histamine, norepinephrine, and serotonin in the frontal cortex of mice. Methods: Samples for measuringhistamine, norepinephrine, and serotonin contents were collected by in vivomicrodialysis of the frontal cortex of anesthetized mice. histamine, noradrenaline, and serotonin content in dialysates were measured by HPLC techniques. Results: Intracrebroventricular injection of orexin A at doses of 12.5, 50, and 200 pmol per mouse promoted histamine release from the frontal cortex ina dose-dependent manner. At the highest dose given, 200 pmol, orexin A signifi-cantly induced histamine release, with the maximal magnitude being 230% overthe mean basal release. The enhanced histamine release was sustained for 140min, and then gradually returned to the basal level. However, no change in nore -pinephrine or serotonin release was observed under application of the same dose of orexin A. Confluence: These results suggest that the arousal effect of orexin Ais mainl y mediated by histamine, not by norepinephrine or serotonin.