Effect of microinjection of orexin-A and orexin-B into cerebral ventricle on the release of histamine in hypothalamus / 临床麻醉学杂志

ABSTRACT

Objective To provide new evidences for understanding the mechanisms of promo-tive role of orexins in anesthetic emergence and the effect of microinjection of orexin-A/orexin-B into cerebral ventricle on the release of histamine.Methods Male SD rats were randomly divided into sa-line (control ), orexin-A and orexin-B groups. The microdialysis probe was inserted into hypothalamus under stereotaxic apparatus.The perfused fluid from the area of hypothalamic tube-romammillary nucleus was collected using in vivo microdialysis at 1 h,2 h and 3 h after 1 nmol or 5 nmol orexin-A or orexin-B microinjection into the cerebral ventricle (n =5 each).The concentrations of histamine at each time point in dialysates of perfused fluid were detected by high performance liquid chromatography (HPLC)to analyze its dynamic changes.After one week,each group was microin-jected with 10 nmol,15 nmol and 20 nmol orexin-A and orexin-B (n =5)into the cerebral ventricle respectively,dialysates was collect and histamine was detected at 1 h to analyze its dosage response. After one week,each group was microinjected 0.3 μl saline orexin-A and orexin-B (n =6)into the tu-beromammillary nucleus.Results Compared with the control group,microinjection of 1 nmol orexin-A significantly increased histamine release at 1 h,but the same dose of orexin-B had no such effect,5 nmol of orexin-A or orexin-B injections significantly facilitated histamine release at 2 h and 3 h (P <0.01).Microinjection of 10 nmol,15 nmol and 20 nmol orexin-A and orexin-B into ventricle caused an significant increase of histamine release at 1 h while the effect was the strongest in 20 nmol (P <0.05).Compared with the control group,microinjection of orexin-A significantly decreased time of the righting reflex (P <0.01),but the same dose of orexin-B had no such effect.Conclusion Micro-injection of both orexin-A or orexin-B into cerebral ventricle could promote the release of histamine, while the effect of orexin-A was stronger.Microinjection orexin-A into tuberomammillary nucleus sig-nificant facilitated recovery from isoflurane.