Objective: To observe effects of orexin on wakefulness and content of norepinephrine(NE)

serotonin(5-HT) in hypothalamus to discuss the mechanisms. Method: Rats were divided into the control group

the model group

the low-dose group and the high-dose group at random. Each group included 10 rats.The anesthesia rat model was established with intraperitoneal injection by using chloral hydrate and urethane mixture(1:1)according to 5 mL·kg-1. The low-dose group were intraperitoneally injected orexin 10 μL (1 mmol·L-1

0.1 mg)from paracele and the high-dose group were intraperitoneal injected orexin 10 μL (5 mmol·L-1

0.5 mg)from paracele. To observe lost of righting reflex(LORR) time and LORR lasting time. ELISA method was applied to test content of NE

5-HT in hypothalamus. Result: Compared with the control group

in the model group the content of both NE[(82.44±2.16) ng·L-1] and 5-HT[(149.88±14.21) ng·L-1] declined

but there was no significant difference. Compared with the model group by content of NE in the high-dose group the content of NE[(158.83±4.87) ng·L-1] increased significantly(P<0.01).Compared with the model group by content of 5-HT [(149.88±14.21) ng·L-1]

in the low-dose group the content of 5-HT [(232.58±16.05) ng·L-1] increased (P<0.05) and in the high-dose group the content of 5-HT [(278.14±17.85[BFQ])ng·L-1] increased significantly(P<0.01). Compared with the model group by LORR lasting time [(61.08±11.32) min]

in the high-dose group [(32.01±7.42) min] reduced significantly(P<0.01). Conclusion: orexin could excite NE

5-HT neuron

which enhance cerebral cortex effect of ‘facilitatioin’ on monamine neuron

finally may cause and keep wakefulness

which is probably one of the mechanisms of orexin causing wakefulness.