Gajewska A, Zwierzchowski L, Kochman K
Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jablonna, Poland.
J Neuroendocrinol. 2004 Jun;16(6):558-65. doi: 10.1111/j.1365-2826.2004.01202.x.
Although galanin, which exerts its effects both at the hypothalamic and pituitary level, has been implicated as an important neuroendocrine regulator of hypothalamic-pituitary-gonadal axis activity, there is a lack of data concerning its involvement in the regulation of gonadotropin subunit gene expression. To elucidate whether galanin can influence luteinizing hormone (LH) subunit mRNA content, as well as affect gonadotropin-releasing hormone (GnRH) receptor activity, a model based on pulsatile (one pulse per hour over 5 h) galanin (1 nM) microinjections directly into the third cerebral ventricle of ovariectomized (OVX) and/or oestrogen/progesterone-pretreated rats was used. Furthermore, to determine galanin effects on GnRH-induced LH subunit mRNA synthesis, a cocktail of 1 nM GnRH and 1 nM galanin was coadministered in a pulsatile manner to OVX/steroid primed rats. Subsequently, to obtain data concerning the role of galanin receptors in the regulation of pituitary alpha (common to LH, follicle-stimulating hormone, thyroid-stimulating hormone) and LHbeta subunit gene expression, OVX/oestrogen/progesterone rats received microinjections of 1 nM of the receptor antagonist galantide and 1 nM of galanin. In this case, both substances were administered separately, with a 30 min lag, according to which each galantide pulse always preceded a galanin pulse. Northern-blot analysis revealed that intracerebroventricular pulsatile galanin injections were effective in stimulation of both alpha and LHbeta subunit mRNA levels and that this effect was apparently steroid-dependent. Moreover, galanin also up-regulated GnRH receptor functional parameters (affinity and maximum binding capacity) but was ineffective in potentiating GnRH-induced accumulation of both subunit mRNAs. The results from the study also indicate that galanin acts through its own receptor(s) because a receptor antagonist, galantide, significantly reduced the stimulatory effect exerted by galanin on the expression of both LH subunit genes in vivo.
尽管甘丙肽在下丘脑和垂体水平均发挥作用，且已被认为是下丘脑-垂体-性腺轴活动的重要神经内分泌调节因子，但关于其参与促性腺激素亚基基因表达调控的数据却很缺乏。为了阐明甘丙肽是否能影响促黄体生成素（LH）亚基的mRNA含量，并影响促性腺激素释放激素（GnRH）受体活性，采用了一种模型，即对去卵巢（OVX）和/或经雌激素/孕酮预处理的大鼠，每小时一次脉冲式（共5小时）向第三脑室直接微量注射1 nM甘丙肽。此外，为了确定甘丙肽对GnRH诱导的LH亚基mRNA合成的影响，以脉冲方式将1 nM GnRH和1 nM甘丙肽的混合物共同给予OVX/类固醇预处理的大鼠。随后，为了获得关于甘丙肽受体在垂体α亚基（LH、促卵泡激素、促甲状腺激素所共有的）和LHβ亚基基因表达调控中作用的数据，给OVX/雌激素/孕酮大鼠微量注射1 nM的受体拮抗剂丙谷酰胺和1 nM甘丙肽。在这种情况下，两种物质分别给药，间隔30分钟，即每次丙谷酰胺脉冲总是先于甘丙肽脉冲。Northern印迹分析显示，脑室内脉冲式注射甘丙肽可有效刺激α亚基和LHβ亚基的mRNA水平，且这种作用显然依赖于类固醇。此外，甘丙肽还上调了GnRH受体功能参数（亲和力和最大结合能力），但在增强GnRH诱导的两个亚基mRNA积累方面无效。该研究结果还表明，甘丙肽通过其自身的受体发挥作用，因为受体拮抗剂丙谷酰胺显著降低了甘丙肽在体内对两个LH亚基基因表达的刺激作用。
