Aguilar-Roblero Raúl, González-Mariscal Gabriela
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Centro de Investigación en Reproducción Animal, CINVESTAV-Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
Eur J Neurosci. 2020 Jan;51(1):429-453. doi: 10.1111/ejn.14265. Epub 2018 Dec 14.
Adult rabbits show robust circadian rhythms of: nursing, food and water intake, hard faeces excretion, locomotion, body temperature, blood and intraocular pressure, corticosteroid secretion, and sleep. Control of several circadian rhythms involves a light-entrained circadian clock and a food-entrained oscillator. Nursing periodicity, however, relies on a suckling stimulation threshold. Brain structures regulating this activity include the paraventricular nucleus and preoptic area, as determined by lesions and quantification of cFOS- and PER1 clock gene-immunoreactive proteins. Melatonin synthesis in the rabbit pineal gland shows a diurnal rhythm, with highest values at night and lowest ones during the day. In kits the main zeitgeber is milk intake, which synchronizes locomotor activity, body temperature, and corticosterone secretion. Brain regions involved in these effects include the median preoptic nucleus and several olfactory structures. As models for particular human illnesses rabbits have been valuable for studying glaucoma and cardiovascular disease. Circadian variations in intraocular pressure (main risk factor for glaucoma) have been found, with highest values at night, which depend on sympathetic innervation. Rabbits fed a high fat diet develop cholesterol plaques and high blood pressure, as do humans, and such increased fat intake directly modulates cardiovascular homeostasis and circadian patterns, independently of white adipose tissue accumulation. Rabbits have also been useful to investigate the characteristics of sleep across the day and its modulation by infections, cytokines and other endogenous humoral factors. Rabbit circadian biology warrants deeper investigation of the role of the suprachiasmatic nucleus in regulating most behavioral and physiological rhythms described above.
成年兔子表现出多种强大的昼夜节律，包括：哺乳、食物和水的摄入、硬粪排泄、运动、体温、血压和眼压、皮质类固醇分泌以及睡眠。几种昼夜节律的控制涉及一个受光调节的昼夜节律钟和一个受食物调节的振荡器。然而，哺乳周期依赖于一个哺乳刺激阈值。通过损伤以及对cFOS和PER1生物钟基因免疫反应蛋白的定量分析确定，调节这种活动的脑结构包括室旁核和视前区。家兔松果体中的褪黑素合成呈现昼夜节律，夜间值最高，白天值最低。在幼兔中，主要的授时因子是乳汁摄入，它可使运动活动、体温和皮质酮分泌同步。参与这些效应的脑区包括视前正中核和几个嗅觉结构。作为特定人类疾病的模型，兔子在研究青光眼和心血管疾病方面具有重要价值。已发现眼压（青光眼的主要危险因素）存在昼夜变化，夜间值最高，这取决于交感神经支配。与人类一样，喂食高脂肪饮食的兔子会形成胆固醇斑块和高血压，这种脂肪摄入量的增加直接调节心血管稳态和昼夜模式，与白色脂肪组织的积累无关。兔子在研究全天睡眠特征及其受感染、细胞因子和其他内源性体液因子调节方面也很有用。兔子的昼夜生物学值得深入研究视交叉上核在调节上述大多数行为和生理节律中的作用。
