Department of Animal Science, University of Minnesota, St Paul, MN 55108, USA.
J Neuroendocrinol. 2010 Feb;22(2):119-28. doi: 10.1111/j.1365-2826.2009.01942.x. Epub 2009 Dec 4.
The premammillary nucleus (PMM) has been shown to contain a daily endogenous dual-oscillation in dopamine (DA)/melatonin (MEL) as well as c-fos mRNA expression that is associated with the daily photo-inducible phase of gonad growth in turkeys. In the present study, the expression of clock genes (Bmal1, Clock, Cry1, Cry2, Per2 and Per3) in the PMM was determined under short (8 : 16 h light/dark cycle) and long (16 : 8 h light/dark cycle) photoperiods relative to changes associated with the diurnal rhythm of DA and MEL. Constant darkness (0 : 24 h light/dark cycle) was used to assess the endogenous response of clock genes. In addition, light pulses were given at zeitgeber time (ZT) 8, 14 and 20 to ascertain whether clock gene expression is modulated by light pulse stimulation and therefore has a daily phase-related response. In the PMM, the temporal clock gene expression profiles were similar under short and long photoperiods, except that Per3 gene was phase-delayed by approximately 16 h under long photoperiod. In addition, Cry1 and Per3 genes were light-induced at ZT 14, the photosensitive phase for gonad recrudescence, whereas the Clock gene was repressed. Gene expression in established circadian pacemakers, the visual suprachiasmatic nucleus (vSCN) and the pineal, was also determined. Clock genes in the pineal gland were rhythmic under both photoperiods, and were not altered after light pulses at ZT 14, which suggests that pineal clock genes may not be associated with the photosensitive phase and reproductive activities. In the vSCN, clock gene expression was phase-shifted depending on the photoperiod, with apexes at night under short day length and during the day under long day length. Furthermore, light pulses at ZT 14 induced the Per2 gene, whereas it repressed the Bmal1 gene. Taken together, the changes in clock gene expression observed within the PMM were unique compared to the pineal and vSCN, and were induced by long photoperiod and light during the daily photosensitive phase; stimuli that are also documented to promote reproductive activity. These results show that Cry1 and Per3 are involved in the photic response associated with the PMM neuronal activation and are coincident with an essential circadian mechanism (photosensitive phase) controlling the reproductive neuroendocrine system.
已发现前乳突核（PMM）中多巴胺（DA）/褪黑素（MEL）的内源性双重振荡以及 c-fos mRNA 表达存在每日节律，这与火鸡的性腺生长的每日光诱导阶段有关。在本研究中，根据与 DA 和 MEL 的昼夜节律变化相关，确定了 PMM 中时钟基因（Bmal1、Clock、Cry1、Cry2、Per2 和 Per3）在短光照（8:16 h 光/暗周期）和长光照（16:8 h 光/暗周期）条件下的表达。使用持续黑暗（0:24 h 光/暗周期）来评估时钟基因的内源性反应。此外，在 Zeitgeber 时间（ZT）8、14 和 20 给予光脉冲，以确定时钟基因表达是否受光脉冲刺激调制，因此具有与每日相位相关的反应。在 PMM 中，短光照和长光照条件下的时间时钟基因表达谱相似，除了长光照条件下 Per3 基因大约延迟 16 h 外。此外，Cry1 和 Per3 基因在光敏感阶段 ZT14 时被光诱导，而 Clock 基因受到抑制。还确定了已建立的生物钟起搏器视交叉上核（vSCN）和松果体中的基因表达。松果体中的时钟基因在两种光照条件下均呈节律性，并且在 ZT14 的光脉冲后不会改变，这表明松果体时钟基因可能与光敏感阶段和生殖活动无关。在 vSCN 中，时钟基因的表达根据光照周期发生相位移动，在短光照下夜间达到高峰，在长光照下白天达到高峰。此外，ZT14 时的光脉冲诱导 Per2 基因，而抑制 Bmal1 基因。总之，与松果体和视交叉上核相比，PMM 中观察到的时钟基因表达变化是独特的，并且由长光照和白天的光诱导，以及促进生殖活动的记录刺激诱导。这些结果表明，Cry1 和 Per3 参与与 PMM 神经元激活相关的光反应，并与控制生殖神经内分泌系统的基本生物钟机制（光敏感阶段）一致。
