光照周期对褪黑激素受体在母兔下丘脑-垂体-卵巢轴中分布与表达的影响

doi:10.11843/j.issn.0366-6964.2019.12.016

摘要/Abstract

摘要： 旨在观察不同光照周期对新西兰白色母兔褪黑激素受体在"下丘脑-垂体-性腺轴"中的分布和表达模式，从而进一步分析褪黑激素在不同光照周期下调控母兔发情的机制。选用5月龄未经产新西兰母兔48只，随机分成3组，每组16只，前10 d各试验组采用"12 h光照：12 h黑暗"的光照制度，后6 d分别采用长光照（16 h光照：8 h黑暗）、短光照（8 h光照：16 h黑暗）和正常光照（12 h光照：12 h黑暗，对照组）的光照制度，光照强度80 lx，试验期为16 d。试验结束后剖杀动物，取下丘脑、垂体和卵巢，用qPCR、免疫印迹、免疫组织化学方法，研究不同光照周期对母兔的下丘脑、垂体、卵巢中褪黑激素受体亚型分布与表达的影响。结果表明：在下丘脑，短光照组的MT1 mRNA表达量较长光照组高88.8%（P<0.05），较对照组高54.9%（P<0.05），长光照组与对照组间无显著差异；MT2 mRNA表达量在不同光周期组间差异不显著（P>0.05）。免疫组织化学染色结果显示，长光照组下丘脑室周核的MT1阳性细胞数明显较短光照组少69.4%（P<0.05），较对照组少37.3%（P<0.05），短光照组比对照组显著多104.8%（P<0.05）；同样，长光照组室旁核的MT1阳性细胞数明显较短光照组少52.9%（P<0.05），对照组明显较短光照组少55.8%（P<0.05），而长光照组与对照组间差异不显著（P>0.05）。在垂体，短光照组的MT1 mRNA表达量比长光照组显著高164%（P<0.05），比对照组显著高49.5%（P<0.05），而长光照组比对照组显著低43.5%（P<0.05）；但不同光周期下MT2 mRNA表达量差异不显著（P>0.05）；长光照组的卵巢MT1 mRNA表达量较对照组低33.3%（P<0.05），较短光照组低53.6%（P<0.05），短光照组与对照组间差异不显著（P>0.05）；卵巢中短光照组MT2的mRNA相对表达量比对照组显著高90.0%（P<0.05），比长光照组显著高100%（P<0.05），长光照组与对照组差异不显著（P>0.05）。短光照周期显著提高了下丘脑、垂体和卵巢中褪黑激素受体亚型MT1表达，而不是MT2受体亚型。光照周期调控母兔发情的作用机制可能是褪黑激素通过MT1受体途径实现的。

关键词: 光照周期, 兔, 下丘脑, 垂体, 卵巢, MT1, MT2

Abstract: The purpose of the study was to investigate the effect of photoperiods on the distribution and expression patterns of melatonin receptor in the "hypothalamic-pituitary-gonadal axis" of female rabbits, and to further analyze the mechanism of melatonin regulating estrus in female rabbits under different photoperiods. A total of 48 5-month-old nulliparous female New Zealand rabbits, were reared in artificial illumination. They were randomly assigned to 3 groups of 16 each. All groups were reared in 12-h L/12-h D photoperiod for the first 10 days, then were reared in long light group (LD, L:D=16:8), short light group (SD, L:D=8:16) or control group (L:D=12:12) for the last 6 days separately. Light intensity was 80 lx, the total trial period was 16 days. The hypothalamus, pituitary and ovary samples were collected after the test. The effects of photoperiod on the distribution and expression of melatonin receptor subtypes in hypothalamus, pituitary and ovaries of female rabbits were investigated by real-time PCR, Western blot and immunohistochemical staining. The results showed that the expression of MT1 mRNA in the SD group was 88.8% higher than that in the LD group (P<0.05), and 54.9% higher than that in the control group (P<0.05), but there was no significant difference between the LD group and the control group. The expression of MT2 mRNA was not significantly different between different photoperiod groups (P>0.05). Immunohistochemical staining showed that the number of MT1 positive cells in the periventricular nucleus of the hypothalamus in the LD group was significantly lower than that in the SD group (69.4%, P<0.05) and the control group (37.3%, P<0.05), and that of SD group was 104.8% higher (P<0.05) than the control group. Meanwhile, the number of MT1 positive cells in the paraventricular nucleus of the LD group was 52.9% lower than that in the SD group (P<0.05), and that of the control group was 55.8% lower than that of the SD group (P<0.05), while there was no difference between the LD group and the control group (P>0.05). In the pituitary, the expression of MT1 mRNA in the SD group was 164% higher than that in the LD group (P<0.05) and 49.5% higher than that in the control group (P<0.05), and the LD group was significantly lower than the control group by 43.5% (P<0.05), while there was no significant difference in MT2 mRNA expression between different photoperiods (P>0.05). The expression of MT1 mRNA in the ovary of the LD group was 33.3% lower than that of the control group (P<0.05) and 53.6% lower than that of the SD group (P<0.05), and there was no significant difference between the SD group and the control group (P>0.05). However, the relative mRNA expression of MT2 of the ovary in the SD group was significantly higher than that of the control group by 90.0% (P<0.05) and the LD group by 100% (P<0.05), and there was no difference between the LD group and the control group (P>0.05). Short light photoperiod increased the expression of melatonin receptor MT1 subtype in hypothalamus, pituitary gland and ovary, rather than the MT2 receptor. These results suggest that the regulation mechanism of photoperiod on estrus in female rabbits may be realized by MT1 receptor pathway.

Key words: photoperiod, rabbit, hypothalamus, pituitary, ovary, MT1, MT2

中图分类号:

S852.16

王文利, 张玉仙, 原展航, 王子旭, 董玉兰, 陈耀星. 光照周期对褪黑激素受体在母兔下丘脑-垂体-卵巢轴中分布与表达的影响[J]. 畜牧兽医学报, 2019, 50(12): 2518-2528.

WANG Wenli, ZHANG Yuxian, YUAN Zhanhang, WANG Zixu, DONG Yulan, CHEN Yaoxing. Effect of Photoperiods on Distribution and Expression of Melatonin Receptors in Hypothalamus-Pituitary-Ovary Axis in Female Rabbits[J]. Acta Veterinaria et Zootechnica Sinica, 2019, 50(12): 2518-2528.

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