- 學位論文
食慾素於視神經交叉上核所造成的睡眠清醒節律改變所扮演的角色
The Role of Suprachiasmatic Nucleus (SCN) Orexin/Hypocretin in the Alternation of Sleep Circadian Fluctuation
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摘要
約日節律是一種動物於分子層面、生理反應及行為表現出來的24小時節律。控制哺乳類動物約日節律的腦區位於視神經交叉之上，稱為視神經交叉上核 (su- prachiasmatic nucleus；SCN)。SCN是藉由節律基因以及節律蛋白的互相調控下呈現規律的約日節律。食慾素為一新興激素，於動物控制食慾的腦區，也就是側下視丘 (lateral hypothalamus；LHA) 所分離到，最主要的生理功能為促進動物進食及保持警醒。食慾素擁有兩個subtypes，分別為orexin A/hypocretin-1 及orexin B/hypocretin-2。同樣的，也有兩種食慾素G protein-coupled receptors。Orexin A receptor/Hypocretin receptor 1屬於Gq protein，至於orexin B receptor/hypocretin receptor 2屬於Gi/Go亦或Gq protein。近期的研究報告指出，SCN上具有OX1R/ HcrtR1的存在。 根據本實驗室之前的研究結果指出，於zeitgeber time (ZT) 6在杏仁核進行電刺激模擬顳葉型癲癇 (temporal lobe epilepsy；TLE) 發作後，會造成大鼠約日節律中的睡眠－清醒週期向前平移兩個小時的情形。此情形可以藉由在SCN顯微注射orexin A/hypocretin-1的拮抗劑後被阻斷。因此，本實驗模擬TLE所造成的結果，直接在SCN進行顯微注射orexin A/hypocretin-1後觀察睡眠－清醒週期是否產生改變，並進一步探討造成此週期改變的細胞內訊息傳遞路徑。 本實驗主要分成三組，group 1使用磷脂酶C抑制劑 (phospholipase C inhibitor；PLCI) 處理大鼠、group 2使用蛋白激酶C抑制劑 (protein kinase C inhibitor；PKCI) 處理大鼠及group 3使用肌醇三磷酸接受器阻斷劑 (inositol trisphosphate receptor blocker；IP3RB) 處理大鼠。使用Sprague-Dawley公鼠使其適應12:12小時的光暗週期後，於亮期中點ZT 6進行group 1及group 2實驗操弄。於暗期中點ZT 18進行group 3實驗操弄。 於ZT 6注射高劑量orexin A/hypocretin-1 (10 μg/μL) 後，會使group 1大鼠於ZT 6、22與下一個睡眠－清醒週期ZT’ 14及ZT’ 22產生改變；於group 2使ZT 6、ZT 9、ZT 12及下一個睡眠－清醒週期ZT’ 2產生改變。而這些改變可藉由給予orexin A/hypocretin-1前15分鐘顯微注射PLCI及PKCI至SCN而部分阻斷。於ZT 18給予高劑量orexin A/hypocretin-1除了在ZT 18的時間點產生改變外，對於之後的睡眠－清醒週期並不會產生改變，因此給予orexin A/hypocretin-1前15分鐘給予IP3RB後，對於睡眠－清醒週期並無產生任何改變。 實驗結果顯示，於ZT 6顯微注射orexin A/hypocretin-1與杏仁核電刺激所造成的睡眠－清醒週期改變模式不同。而此一改變可藉由給予orexin A/hypocretin-1前15分鐘顯微注射PLCI及PKCI被部分阻斷，顯示造成大鼠睡眠－清醒週期的改變是透過位於SCN上的 OX1R/HcrtR1活化下游phosphatidylinositol turnover (PI turnover) 中的portein kinase C去影響SCN。由於睡眠－清醒週期改變並不會被PLCI及PKCI完全阻斷，推測應還有其它訊息傳遞路徑涉及其中。
並列摘要
Circadian rhythm is endogenously driven a 24-hour cycle in biochemical, phys- iological and behavioral processes in animals. Suprachiasmatic nucleus (SCN) of the hypothalamus is the pacemaker controlling circadian rhythms in mammals. The late- ral hypothalamic area (LHA) involves in the homeostatic regulation of sleep-wake rhythmicity. The neuropeptide secreted from LHA is orexin/hypocretin, which is an arousal and feeding promoter. Orexin/hypocretin possesses two forms, orexin A/hypo- cretin-1 and orexin B/hypocretin-2. Likewise, there are two types of G-protein coup- led receptors for orexin/hypocretin. Orexin A receptor/Hypocretin receptor 1 (OX1R/ HcrtR1) is coupled to the Gq protein, while orexin B receptor/hypocretin receptor 2 (OX2R/HcrtR2) is coupled to the Gi/Go or Gq protein. Moreover, orexinergic/hypocr- etinergic fibers and receptor expressions are discovered in the SCN region. Only OX1R/HcrtR1 presents in the SCN. Our previous results demonstrated that the sleep circadian in rats with temporal lobe epilepsy (TLE) shifted 2 hours in advance. This circadian alternation was blocked by microinjection of OX1R/HcrtR1 antagonist into the SCN. Therefore, we mimicked the TLE effect by microinjection of orexin A/hyp- ocretin-1 into the SCN. Male Sprague-Dawley rats were housed in a 12:12-hour light:dark cycle. The experiments were devided into 3 groups. In group 1, rats were treated by phospholip- ase C inhibitor (PLCI). In group 2, rats were treated by protein kinase C inhibitor (PKCI). In group 3, rats were treated by inositol trisphosphate receptor blocker (IP3RB). In group 1 and group 2, we injected orexin A/hypocretin-1 into the SCN at ZT 6. In group 3, we injected orexin A/hypocretin-1 into the SCN at ZT 18. Electro- encephalogram-defined sleep-wake activity were collected. In group 1, the amount of non-rapid eye movement sleep (NREMS) after 10 μg/μL orexin A/hypocretin-1 microinjection at ZT 6 was altered at ZT 6, ZT 22, ZT’ 14 and ZT’ 22. In group 2, the amount of NREMS after 10 μg/μL orexin A/hypocret- in-1 microinjection at ZT 6 was altered at ZT 6, ZT 9, ZT 12 and ZT’2. In group 3, the amount of NREMS after 10 μg/μL orexin A/hypocretin-1 microinjection at ZT 18 was altered at ZT 18. Our results demonstrated that microinjection of orexinA/hypocretin-1 into the SCN at ZT 6 altered the sleep-wake rhythmicity in rats. Furthermore, this circadian alternation was partly blocked by microinjection of PLCI and PKCI into the SCN. The result suggests that the altered circadian is mediated by the phosphatidylinositol turnover (PI turnover) activated through the HcrtRs but is not dominant in mainten- ance phase.
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延伸閱讀
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- 許筠（2016）。The Effect of Cell Cycle Regulation on Neural Stem CellDevelopment in SCN1A Mutation〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU201602392
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