大鼠松果体Clock基因和芳烷脘N-乙酰基转移酶基因的昼夜节律性表达及光照影响

探讨12h光照、12h黑暗交替(12h-light：12h-dark cycle,LD)及持续黑暗(constant darkness,DD)光制下松果体Clock基因和芳烷脘N-乙酰基转移酶基因(arylalkylamine N-acetyltransferase gene,NAT)是否存在昼夜节律性表达及其光反应变化。Sprague-Dawley大鼠在LD和DD光制下分别被饲养4周(n=36)和8周(n=36)后,在一昼夜内每隔4h采集一组松果体组织(n=6),提取总RNA,用竞争性定量RT-PCR测定不同昼夜时点样品中Clock及NAT基因的mRNA相对表达量,通过余弦法和ClockLab软件获取节律参数,并经振幅检验是否存在昼夜节律。结果如下：(1)在DD或LD光制下,松果体Clock和NAT基因mRNA的表达均呈现夜高昼低的节律性振荡(P＜0．05)。(2)与DD光制下比较,LD光制下松果体Clock和NAT基因的表达振幅及峰值相的mRNA水平均降低(P＜0．05)。(3)在DD或LD光制下,Clock和NAT基因之间显示相似的节律性表达(P＞0．05)。结果表明,Clock和NAT基因在松果体中存在同步的内源性昼夜节律表达,光照作用可使其表达下调。     

哺乳动物昼夜节律组构中的下丘脑视交叉上核和松果腺

哺乳动物下丘脑视交叉上核（SCN）是昼夜节律最主要的起搏器,控制着机体的生理和行为的节律。它具有自身内在的节律性,同时也受光照周期信号和一些内源性化学物质的调节。检查腺分泌裉黑素（MEL）受SCN的调控,MEL通过作用于SCN上高亲和性MEL受体,启动第二、第三信使系统,调整SCN的昼夜节律活动。这种调整具有时间敏感性。     

树Qu尿中皮质醇浓度的昼夜节律及其在视交叉上核损毁后的变化

用放射免疫方法对连续采集的正常树Ｑｕ及视交叉上核损毁树Ｑｕ尿中的皮质醇进行了测定,以分析其尿中皮质醇浓度及排泄量的昼夜变化规律,结果表明,正常树Ｑｕ尿中皮质醇的浓度及单位时间内在排泄均具有明显的昼夜节律,在一天中,１１：００前后的浓度最高,０：００前后的浓度最低,前者约为８倍,视交叉上核损毁后,树Ｑｕ皮质醇的这种昼夜节律消失,说明视交叉上核在树Ｑｕ中也是机体昼夜节律重要的振荡器。     

树Qu排尿的昼夜节律及其在视交叉上核损毁后的变化

显探讨树Ｑｕ视交叉上核是否参与泌尿昼夜节律的调控,对正常树Ｑｕ及视交叉上核损毁后的树Ｑｕ排尿的昼夜时间规律进行了观测分析。结果表明,正常树Ｑｕ排尿呈现明显的昼夜节律－－白天尿量为全天尿量的（８８．５２±１５．０４）％;视交叉上核损毁后,树Ｑｕ排尿的昼夜节律明显改变－白天尿量仅为全天尿量的（６２．８６±１８．１８）％,同时树Ｑｕ的尿量（特别是夜间的尿量）明显增多。以上结果说明视交叉上核在树Ｑｕ体内也     

视交叉上核的内源性昼夜节律以及光,谷氨酸和NO的调制作用

自从发现视交叉上核（ＳＣＮ）中有直接的视网膜下丘脑投射纤维以来,ＳＣＮ的内源性节律及其调节机制受到广泛重视,已成为令人感兴趣的新课题。哺乳动物的２４ｈ昼夜节律而言,ＳＣＮ是主要的启步者,但ＳＣＮ内源性的振荡节律又受到环境光暗周期、谷氨酸和一氧化氮的拖拽。     

树■排尿的昼夜节律及其在视交叉上核损毁后的变化

为探讨树视交叉上核是否参与泌尿昼夜节律的调控,对正常树及视交叉上核损毁后的树排尿的昼夜时间规律进行了观测分析。结果表明,正常树排尿呈现明显的昼夜节律———白天尿量为全天尿量的（８８５２±１５４０）％;视交叉上核损毁后,树排尿的昼夜节律明显改变———白天尿量仅为全天尿量的（６２８６±１８１８）％,同时树的尿量（特别是夜间的尿量）明显憎多。以上结果说明视交叉上核在树体内也参与了泌尿昼夜节律的调节。     

树尿中皮质醇浓度的昼夜节律及其在视交叉上核损毁后的变化

用放射免疫方法对连续采集的正常树及视交叉上核损毁树尿中的皮质醇进行了测定,以分析其尿中皮质醇浓度及排泄量的昼夜变动规律。结果表明,正常树尿中皮质醇的浓度及单位时间内的排泄量均具有明显的昼夜节律,在一天中,１１００前后的浓度最高,０００前后的浓度最低,前者约为后者的８倍。视交叉上核损毁后,树皮质醇的这种昼夜节律消失,说明视交叉上核在树中也是机体昼夜节律重要的振荡器。     

褪黑素对大鼠下丘脑薄片视交叉上核神经元放电昼夜节律性的调制

先用持续光照和松果腺切除预处理大鼠,然后制成下丘脑薄片,记录其视交叉上核（ＳＣＮ）神经元自发放电,观察其昼夜变化和褪黑素（ＭＥＬ）对它的影响。实验结果表明：⑴在正常光照（光照：黑暗＝１２：１２）条件下,ＳＣＮ神经元自发放电频率呈现昼夜低的节律性。在昼夜时间（ＣＴ）６－８出现放电高峰,频率约为８．３Ｈｚ;在ＣＴ１８－２０出现低谷,频率约为３．８Ｈｚ。松果腺切除后,ＳＣＮ神经元自发放电的昼夜节律性基本     

大鼠交叉上核中SS和VIPmRNA昼夜节律的研究

用Ｎｏｒｔｈｅｒｎｂｌｏｔ杂交方法分析ＬＤ循环条件下大鼠ＳＣＮ和ＣＸ的ＳＳｍＲＮＡ和ＶＩＰｍＲＮＡ丰度的昼夜变化，结果表明这两种ｍＲＮＡ昼夜间的相对含量在ＣＸ中基本不变，而在ＳＣＮ中则呈现规律性变化的模式，与双侧眼球摘除后大鼠ＳＣＮｍＲＮＡ丰度昼夜变化的实验结果相比较，ＳＳｍＲＮＡ丰度变化不受外界光的影响，具有内源性的昼夜节律，而ＶＩＰｍＲＮＡ丰度的昼夜变化则受外界光的影响。     

大鼠下丘脑交叉上核中CREB的昼夜节律

利用凝胶迁移率变化的实验方法,对饲养在光照－黑暗循环的条件和持续黑暗的条件下Wistar雄性大鼠下丘脑交叉上核中CREB含量的昼夜间变化进行了分析,发现CREB在交叉上核中具有内源性的昼夜节律.     

Serotonergic innervation of the hypothalamic suprachiasmatic nucleus and photic regulation of circadian rhythms

Converging lines of evidence have firmly established that the hypothalamic suprachiasmatic nucleus (SCN) is a light-entrainable circadian oscillator in mammals, critically important for the expression of behavioral and physiological circadian rhythms. Photic information essential for the daily phase resetting of the SCN circadian clock is conveyed directly to the SCN from retinal ganglion cells via the retinohypothalamic tract. The SCN also receives a dense serotonergic innervation arising from the mesencephalic raphe. The terminal fields of retinal and serotonergic afferents within the SCN are co-extensive, and serotonergic agonists can modify the response of the SCN circadian oscillator to light. However, the functional organization and subcellular localization of 5HT receptor subtypes in the SCN are just beginning to be clarified. This information is necessary to understand the role 5HT afferents play in modulating photic input to the SCN. In this paper, we review evidence suggesting that the serotonergic modulation of retinohypothalamic neurotransmission may be achieved via at least two different cellular mechanisms: 1) a postsynaptic mechanism mediated via 5HT_1A or 5ht₇ receptors located on SCN neurons; and 2) a presynaptic mechanism mediated via 5HT_1B receptors located on retinal axon terminals in the SCN. Activation of either of these 5HT receptor mechanisms in the SCN by specific 5HT agonists inhibits the effects of light on circadian function. We hypothesize that 5HT modulation of photic input to the SCN may serve to set the gain of the SCN circadian system to light.     

Circadian rhythms of indoleamines and serotonin N-acetyltransferase activity in the pineal gland

Conclusion The circadian rhythm of melatonin synthesis in the pineal glands of various species has been summarized. The night-time elevation of melatonin content is in most if not all cases regulated by the change of N-acetyltransferase activity. In mammals, the N-acetyltransferase rhythm is controlled by the central nervous system, presumably by suprachiasmatic nuclei in hypothalamus through the superior cervical ganglion. In birds, the circadian oscillator that regulates the N-acetyltransferase rhythm is located in the pineal glands. The avian pineal gland may play a biological clock function to control the circadian rhythms in physiological, endocrinological and biochemical processes via pineal hormone melatonin.     

Early development of circadian rhythmicity in the suprachiamatic nuclei and pineal gland of teleost,flounder (Paralichthys olivaeus), embryos

Circadian rhythms enable organisms to coordinate multiple physiological processes and behaviors with the earth's rotation. In mammals, the suprachiasmatic nuclei (SCN), the sole master circadian pacemaker, has entrainment mechanisms that set the circadian rhythm to a 24‐h cycle with photic signals from retina. In contrast, the zebrafish SCN is not a circadian pacemaker, instead the pineal gland (PG) houses the major circadian oscillator. The SCN of flounder larvae, unlike that of zebrafish, however, expresses per2 with a rhythmicity of daytime/ON and nighttime/OFF. Here, we examined whether the rhythm of per2 expression in the flounder SCN represents the molecular clock. We also examined early development of the circadian rhythmicity in the SCN and PG. Our three major findings were as follows. First, rhythmic per2 expression in the SCN was maintained under 24 h dark (DD) conditions, indicating that a molecular clock exists in the flounder SCN. Second, onset of circadian rhythmicity in the SCN preceded that in the PG. Third, both 24 h light (LL) and DD conditions deeply affected the development of circadian rhythmicity in the SCN and PG. This is the first report dealing with the early development of circadian rhythmicity in the SCN in fish.     

Lcg is a light-inducible and clock-controlled gene expressed in the chicken pineal gland

The circadian clock is an autonomous biological clock that is entrainable to environmental 24-h cycles by receiving time cues such as light. Generally, light given at early and late subjective night, respectively, delays and advances the phase of the circadian oscillator. We previously searched for the chicken pineal genes that are induced by light in a phase-dependent manner. The present study undertook cDNA cloning and characterization of a gene whose expression was remarkably up-regulated by light at late subjective night. The mRNA level of this gene exhibited robust diurnal change in the pineal gland, with a peak in the early (subjective) day under light-dark cycles and constant dark condition, and hence it was designated Lcg (Light-inducible and Clock-controlled Gene). Chicken Lcg encodes a coiled-coil protein composed of 560 amino acid residues. Among chicken tissues, the pineal gland and the retina exhibited relatively high expression levels of LCG. LCG was colocalized with gamma-tubulin, a centrosomal protein, when expressed in COS7 cells, and LCG is the first example of a clock-related molecule being accumulated at the centrosome. Coimmunoprecipitation of LCG with gamma-tubulin in the chicken pineal lysate suggests a link between the circadian oscillator and the centrosomal function.