Thiery Jean-Claude, Lomet Didier, Schumacher Michael, Liere Philippe, Tricoire Helene, Locatelli Alain, Delagrange Philippe, Malpaux Benoit
UMR INRA-CNRS-Université de Tours, Physiologie de la Reproduction et des Comportements, Nouzilly, France.
J Pineal Res. 2006 Nov;41(4):306-12. doi: 10.1111/j.1600-079X.2006.00370.x.
In the ewe, seasonal anestrus results from an increased responsiveness of the hypothalamus to the negative feedback of estradiol (E2) on the gonadotropic axis under long-day conditions. However, this seasonal effect could also depend upon variable uptake of steroids by the brain. The aim of the present experiment was to compare the concentration of E2 in the blood plasma and in the cerebrospinal fluid (CSF) from the third ventricle in groups of ovariectomized, estradiol treated ewes maintained under short day (SD) or long day (LD) conditions and to study the involvement of the pineal gland in this photoperiodic regulation. Pinealectomized and sham-operated ewes were equipped with an intracerebral cannula to sample the CSF. The plasma E2 concentrations showed no difference between LD and SD in sham-operated and pinealectomized animals. In contrast, in the CSF, E2 concentration was higher in the LD than the SD group, and pinealectomy suppressed this effect of photoperiod. Concomitantly, the stimulatory effect of SD on luteinizing hormone levels observed in sham-operated ewes was abolished by pinealectomy. The results demonstrate that LD increases the E2 concentration in the CSF by a mechanism involving the pineal gland.
在母羊中，季节性发情周期是由于在长日照条件下，下丘脑对促性腺轴上雌二醇（E2）的负反馈反应性增强所致。然而，这种季节性效应也可能取决于大脑对类固醇的不同摄取情况。本实验的目的是比较在短日照（SD）或长日照（LD）条件下饲养的去卵巢、经雌二醇处理的母羊组中，血浆和第三脑室脑脊液（CSF）中E2的浓度，并研究松果体在这种光周期调节中的作用。对松果体切除和假手术的母羊安装脑内插管以采集脑脊液。在假手术和松果体切除的动物中，血浆E2浓度在长日照和短日照之间没有差异。相反，在脑脊液中，长日照组的E2浓度高于短日照组，松果体切除抑制了光周期的这种效应。同时，假手术母羊中观察到的短日照对促黄体生成素水平的刺激作用被松果体切除所消除。结果表明，长日照通过涉及松果体的机制增加脑脊液中E2的浓度。
