Orexin A promotes histamine, but not norepinephrine or serotonin, release in frontal cortex of mice.
OBJECTIVE
To investigate the effects of orexin A on release of histamine, norepinephrine, and serotonin in the frontal cortex of mice.


METHODS
Samples for measuring histamine, norepinephrine, and serotonin contents were collected by in vivo microdialysis of the frontal cortex of anesthetized mice. The 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 in a dose-dependent manner. At the highest dose given, 200 pmol, orexin A significantly induced histamine release, with the maximal magnitude being 230% over the mean basal release. The enhanced histamine release was sustained for 140 min, and then gradually returned to the basal level. However, no change in norepinephrine or serotonin release was observed under application of the same dose of orexin A.


CONCLUSIONS
These results suggest that the arousal effect of orexin A is mainly mediated by histamine, not by norepinephrine or serotonin.
Hong
Zong-Yuan
ZY
School of Life Science, University of Science and Technology of China, Hefei 230027, China.
Huang
Zhi-Li
ZL
Qu
Wei-Min
WM
Eguchi
Naomi
N
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005625:Frontal Lobe / Q000378:metabolism*; D006632:Histamine / Q000378:metabolism*; D007276:Injections, Intraventricular; D047908:Intracellular Signaling Peptides and Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017551:Microdialysis; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D000068797:Orexins; D012701:Serotonin / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D012701:Serotonin; D006632:Histamine; D009638:Norepinephrine