Masumoto Koh-hei, Nagano Mamoru, Takashima Naoyuki, Hayasaka Naoto, Hiyama Hideki, Matsumoto Shun-ichiro, Inouye Shin-Ichi T, Shigeyoshi Yasufumi
Department of Physics, Informatics and Biology, Yamaguchi University, Yoshida, Yamaguchi 753-8512, Japan.
Eur J Neurosci. 2006 Jun;23(11):2959-70. doi: 10.1111/j.1460-9568.2006.04834.x.
The suprachiasmatic nucleus (SCN) is the master circadian clock that regulates physiological and behavioral circadian rhythms in mammals. Prokineticin 2 (PK2) is highly expressed in the SCN, and its involvement in the generation of circadian locomotor activity has been reported previously. In the present study, using in situ hybridization methods, we investigated the localization of PK2 and prokineticin receptor 2 (PKR2), a specific receptor for PK2, in the rat SCN. In steady light : dark (L : D = 12 : 12 h) and constant dark conditions, rPK2 mRNA displayed a robust circadian oscillation with a peak occurring during the day. Moreover, during peak expression, the rPK2 mRNA-positive neurons were scattered in both the dorsomedial and ventrolateral SCN, which are two functionally and morphologically distinct subregions. Furthermore, double-labeling in situ hybridization experiments revealed that greater than 50% of the rPK2 mRNA-containing neurons co-expressed either vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP) or arginine vasopressin (AVP) in the SCN. In contrast, the rPKR2 mRNA levels did not show significant diurnal alterations. rPKR2 mRNA-containing neurons were also clustered in the dorsolateral part of the SCN, which shows negligible labeling of either rAVP, rVIP, rGRP or rPK2 transcripts. In addition, this region exhibited a delayed cycling of the rPer1 gene. These results suggest an intrinsic PK2 neurotransmission and functionally distinct roles for PKR2-expressing neurons in the SCN.
视交叉上核（SCN）是调节哺乳动物生理和行为昼夜节律的主生物钟。前动力蛋白2（PK2）在SCN中高度表达，此前已有报道其参与昼夜运动活动的产生。在本研究中，我们使用原位杂交方法，研究了PK2及其特异性受体前动力蛋白受体2（PKR2）在大鼠SCN中的定位。在稳定的光：暗（L：D = 12：12 h）和持续黑暗条件下，rPK2 mRNA表现出强烈的昼夜振荡，白天出现峰值。此外，在表达峰值期间，rPK2 mRNA阳性神经元分散在背内侧和腹外侧SCN中，这是两个功能和形态上不同的亚区域。此外，双重标记原位杂交实验显示，在SCN中，超过50%的含rPK2 mRNA的神经元共表达血管活性肠肽（VIP）、胃泌素释放肽（GRP）或精氨酸加压素（AVP）。相比之下，rPKR2 mRNA水平没有显示出明显的昼夜变化。含rPKR2 mRNA的神经元也聚集在SCN的背外侧部分，该区域对rAVP、rVIP、rGRP或rPK2转录本的标记可忽略不计。此外，该区域rPer1基因的循环出现延迟。这些结果表明SCN中存在内在的PK2神经传递以及表达PKR2的神经元具有功能上不同的作用。
