| Orexins are recently identified neuropeptides, including OXA and OXB derived from a same prepro-orexin. Orexins are produced mainly in neurons within hypothalamus, then released into cerebrospinal fluid or projected through neuro-fibres to target cells, and consequently activate two types of G-protein coupled receptors, OXR1 and OXR2.90 quails descended from same parents generation were kept in a fixed 12-h light-dark cycle with food and water provided ad libitum for 3w. 10 quails were selected randomly as a group every 3h and brain tissues were fixed with 4% paraformaldehyde, then cut into frozen sections. The 9th group was dealt with the same method after 48h food-inhibition. The sections were stained by immunohistochemical method SABC, and then photograph-analyse software was used in order to study the distribution of OXA in the brainstem of quail and the changes of the relative amount of OXA during 24h, as well as under food-inhibited condition. OXA-immunoreactive (ir) neuronal perikarya were observed within PVN; PVHT; MPH and LHA, OXA-ir axons and their varicose terminals showed a wide spread distribution throughout the whole brainstem of quail. Rhythmic changes in OXA immunostaining were observed during 24h in the TPP; R; DR and LoC associated with the regulation of sleep-wake cycle. The density of OXA-ir neurons within LHA and OXA-ir fibres within some nuclei of brainstem were increased significantly after 48h food-inhibition ( p < 0. 01) , and at the same time, a lot of weak OXA-ir neurons could be observed in DM and DL.These results of the present study suggest that there are different distributions of OXA between in the brainstem of quail and rat, and OXA probably plays an important role in the regulation of food intake, energy homeostasis and sleep-wake cycle.
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