Original Articles

Orexin A promotes histamine, but not norepinephrine or serotonin, release in frontal cortex of mice

Zong-yuan HONG, Zhi-li HUANG, Wei-min QU, Naomi EGUCHI


Aim: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
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.
Conclusion:These results suggest that the arousal effect of orexin A
is mainly mediated by histamine, not by norepinephrine or serotonin.