臺灣博碩士論文加值系統

＂下視丘-腦垂腺-腎上腺軸＂可調控壓力反應。糖皮素進入下視丘與腦垂體後可藉由負回饋機制降低壓力反應。小鼠出生後第一天至第十二天感受壓力的程度極低，這段時間稱之為＂低壓力反應期＂。低壓力反應期的糖皮素含量極低以至於令人懷疑下視丘-腦垂腺-腎上腺軸是否能進行負回饋機制。並且，現今對於此時期下視丘-腦垂腺-腎上腺軸的發育仍待商榷。於此，我們利用Cyp11a1缺失小鼠做為動物模式探討上述問題。於Cyp11a1缺失小鼠（Cyp11a1WT-neo/WT-neo）的腦部與腎上腺，其Cyp11a1表現量減少。進而，發現糖皮素與P5於其腦部、腎上腺以及血流中的含量皆下降。此外，其ACTH含量且於下視丘-腦垂腺-腎上腺軸受到糖皮素所調控的基因,Ｃrh與POMC,皆大幅上升。由此可知，在低壓力反應期其負回饋機制是存在的。並且，Cyp11a1缺失小鼠之腎上腺散亂分布，可知腎上腺發育需有類固醇的存在。

The hypothalamus -pituitary-adrenal axis (HPA axis) is important for stress response. CORT can inhibit the activation of the HPA axis. During mouse development, there is a stress hypo-responsive period (SHRP) at postnatal days 2 to12 when the body does not respond to stress well. It is suspected that CORT level is so low during SHRP that it could not inhibit the HPA axis. However, the development of the HPA axis during this period has not been carefully examined. We studied SHRP using a mouse line deficient in Cyp11a1 (Cyp11a1WT-neo/WT-neo), which encodes an enzyme that catalyzes the first step of steroidogenesis important for the secretion of steroids. Cyp11a1WT-neo/WT-neo mice expressed decreased level of CYP11A1 in adrenal and brain. Their plasma corticosterone (CORT) level was lower and adrenocorticotropic hormone level was higher. The CRH and POMC transcript levels were higher, and CRHR1 mRNA level was lower in Cyp11a1WT-neo/WT-neo mice. These data indicate the HPA axis is inhibited by CORT. Besides, pregnenolone and corticosterone levels in the brain were lower. Furthermore, Cyp11a1WT-neo/WT-neo adrenal was disorganized and smaller compared with the wildtype adrenal. Our results suggest that: (1) Feedback inhibition of the HPA axis was present during SHRP (2) Loss of steroids lead to the disruption of adrenal zonation.

致謝 i
Abbreviations ii
Abstract in Chinese iii
Abstract iv
Table of content v
Introduction P1
1.Steroids P1
Steroidogenesis P1
Classification and function of steroids P1
Neurosteroids P1
The function in Survival and apoptosis P2
The function in neuronal modulation P2
The function in moods P2
2.Neurogenesis P3
Definition P3
Hippocampus P3
3.Adrenal P3
Anatomy P3
Cortex zonation P3
Zonal specific marker in cortex P4
Medulla P4
4.Stress P4
The definition of stress P4
SAS P4
HPA axis activation P5
HPA axis negative feedback for downregulation of stress response P5
5.SHRP P6
The definition of SHRP P6
The maintenance of SHRP P6
Relationship with the hippocampal development P6
6.Steroids and the hippocampus P7
The study in the adulthood P7
Adrenaloctomy P7
Addition of steroids P8
Genetic analysis of animal model P8
The study in the neonatal stage P8
7.Aim and motivation P9
Materials and Methods P10
Mouse line P10
Real-Time PCR P10
Western blotting P10
Perfusion P10
Fixation P11
Sectioning P11
Immunohistochemistry P11
Quanfication of pH3 signals P12
Plasma isolation P12
Steroids extraction P12
Hormone detection P13
Statistical analysis P13
Results P14
The phenotype of Cyp11a1 WT-neo/WT-neo mice P14
Steroid levels were reduced in Cyp11a1WT-neo/WT-neo mice P14
Activated HPA axis in WT-neo mice CYP11A1WT-neo/WT-neo mice P15
The gluconeogenesis was affected in Cyp11a1WT-neo/WT-neo mice after stress during SHRP P16
The steroids deficiency was not affected the brain development P16
The aldosterone synthase, cyp11b2 was increased Cyp11a1WT-neo/WT-neo adrenal P16
Cyp11a1WT-neo/WT-neo adrenal was disorganized and small P17
Discussions P18
The function of Cyp11a1 intron1 containing neo cassette on its transcriptional regulation P18
Low level of steroids effects on early death and feminization P18
Role of steroids in HPA axis during SHRP P19
The regulation of ACTH secretion P20
brain development and steroids P20
The elevated Cyp11b2 level in Cyp11a1WT-neo/WT-neo mice P21
Disorganized and smaller adrenal in Cyp11a1WT-neo/WT-neo mice P21
The different steroids level in Cyp11a1 null mice, Cyp11a1WT-neo/WT-neo mice, and Cyp11a1L/L mice P22
References P24
Tables P29
Figures P31
Supplement P44

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