Ikeno Tomoko, Yan Lily
Department of Psychology, Michigan State University, East Lansing, MI 48824, USA.
Department of Psychology, Michigan State University, East Lansing, MI 48824, USA; Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA.
Brain Res. 2018 Jul 1;1690:89-95. doi: 10.1016/j.brainres.2018.04.002. Epub 2018 Apr 6.
The neuropeptide orexin/hypocretin regulates a wide range of behaviors and physiology through its receptors OX1R and OX2R, or HCRTR-1 and HCRTR-2. Although the distributions of these receptors have been established in nocturnal rodents, their distributions in the brain of diurnal species have not been studied. In the present study, we examined spatial patterns of OX1R and OX2R mRNA expression in diurnal Nile grass rats (Arvicanthis niloticus) by in situ hybridization and compared them with those in nocturnal mice (Mus musculus). Both receptors showed similar spatial patterns between species in most brain regions. However, species-specific expression was found in several regions that are mainly implicated in regulation of sleep/wakefulness, emotion and cognition. OX1R expression was detected in the caudate putamen and ventral tuberomammillary nucleus only in grass rats, while it was detected in the bed nucleus of the stria terminalis, medial division, posteromedial part only in mice. The distribution of OX2R mRNA was mostly consistent between the two species, although it was more widely expressed in the ventral tuberomammillary nucleus in grass rats compared to mice. These results suggest that neuronal pathways of the orexin system differ between chronotypes, and these differences could underlie the distinct profiles in behaviors and physiology between diurnal and nocturnal species.
神经肽食欲素/下丘脑泌素通过其受体OX1R和OX2R（即HCRTR - 1和HCRTR - 2）调节广泛的行为和生理过程。尽管这些受体的分布在夜行性啮齿动物中已得到确定，但它们在昼行性物种大脑中的分布尚未得到研究。在本研究中，我们通过原位杂交检测了昼行性尼罗河草鼠（非洲沼鼠）中OX1R和OX2R mRNA的表达空间模式，并将其与夜行性小鼠（小家鼠）中的模式进行了比较。在大多数脑区中，两种受体在不同物种间显示出相似的空间模式。然而，在几个主要与睡眠/觉醒、情绪和认知调节有关的区域发现了物种特异性表达。仅在草鼠的尾壳核和腹侧乳头体核中检测到OX1R表达，而仅在小鼠的终纹床核内侧部后内侧部分检测到OX1R表达。尽管与小鼠相比，草鼠的腹侧乳头体核中OX2R mRNA的表达更广泛，但两种物种中OX2R mRNA的分布大多一致。这些结果表明，食欲素系统的神经元通路在不同生物钟类型之间存在差异，这些差异可能是昼行性和夜行性物种在行为和生理方面不同特征的基础。
