Gauer F, Masson-Pévet M, Saboureau M, George D, Pévet P
Neurobiologie des Fonctions Rythmiques et Saisonnières, URA-CNRS 1332, Université Louis Pasteur, Strasbourg, France.
J Neuroendocrinol. 1993 Dec;5(6):685-90. doi: 10.1111/j.1365-2826.1993.tb00540.x.
Using quantitative autoradiography, we have studied the seasonal changes of high affinity melatonin receptor density in both the SCN and PT of the hedgehog, a seasonal breeder and an hibernator. Animals in 3 different physiological states were studied: sexually active animals, and sexually inactive animals during the hibernation period, being then either euthermic or hypothermic. In sexually active animals, Bmax were 75.8 +/- 7.1 fmol/mg protein in PT and 9.1 +/- 0.5 fmol/mg protein in SCN; and Kd values were: 94 +/- 22 pM in the PT and 101 +/- 15 pM in the SCN. This specific binding was strongly decreased in the PT of sexually inactive animals. Moreover, this decrease was significantly stronger in hypothermic than in euthermic hedgehogs. Saturation studies and Scatchard analysis revealed that the observed decrease in the PT resulted from change in the Bmax but not in the Kd, Bmax values being respectively 56.4 +/- 5.9 and 29.5 +/- 1.9 fmol/mg protein in euthermic and hypothermic sexually at rest animals. In none of the different physiological states, did the density of melatonin receptors of the SCN show any changes, Bmax values being respectively 9.8 +/- 0.5 and 9.8 +/- 0.4 fmol/mg protein in euthermic and hypothermic sexually at rest animals. This shows for the first time a tissue-specific regulation of melatonin receptor density occurring in the PT but not in the SCN. Furthermore, this decrease of binding in the PT is correlated with both sexual inactivity and hibernation period. This strongly suggests that the mediation of the photoperiodic effect on seasonal functions like seasonal hypothermia and reproduction involves an effect of melatonin on the PT rather than on the SCN.
我们运用定量放射自显影技术，研究了刺猬（一种季节性繁殖动物和冬眠动物）视交叉上核（SCN）和下丘脑室旁核（PT）中高亲和力褪黑素受体密度的季节性变化。我们研究了处于三种不同生理状态的动物：性活跃动物，以及冬眠期的性不活跃动物，后者又分为体温正常和体温过低两种情况。在性活跃动物中，PT的最大结合容量（Bmax）为75.8±7.1 fmol/mg蛋白质，SCN为9.1±0.5 fmol/mg蛋白质；解离常数（Kd）值分别为：PT中94±22 pM，SCN中101±15 pM。在性不活跃动物的PT中，这种特异性结合显著降低。此外，体温过低的刺猬中这种降低比体温正常的刺猬更明显。饱和研究和Scatchard分析表明，PT中观察到的降低是由于Bmax的变化而非Kd的变化，在体温正常和体温过低的性静止动物中，Bmax值分别为56.4±5.9和29.5±1.9 fmol/mg蛋白质。在任何一种不同的生理状态下，SCN的褪黑素受体密度均未显示出任何变化，在体温正常和体温过低的性静止动物中，Bmax值分别为9.8±0.5和9.8±0.4 fmol/mg蛋白质。这首次表明，PT中存在褪黑素受体密度的组织特异性调节，而SCN中没有。此外，PT中结合的减少与性不活跃和冬眠期均相关。这强烈表明，光周期对季节性体温过低和繁殖等季节性功能的影响介导，涉及褪黑素对PT而非SCN的作用。
