Mantei Kristen E, Ramakrishnan Selvakumar, Sharp Peter J, Buntin John D
Department of Biological Sciences, University of Wisconsin-Milwaukee, PO Box 413, Milwaukee, WI 53201, USA.
Horm Behav. 2008 Nov;54(5):669-75. doi: 10.1016/j.yhbeh.2008.07.005. Epub 2008 Jul 29.
Many birds and mammals show changes in the hypothalamo-pituitary-gonadal (HPG) axis in response to social or sexual interactions between breeding partners. While alterations in GnRH neuronal activity play an important role in stimulating these changes, it remains unclear if acute behaviorally-induced alterations in GnRH release are accompanied by parallel changes in GnRH synthesis. To investigate this relationship, we examined changes in the activity of GnRH neurons in the brains of male ring doves following brief periods of courtship interactions with females. Such interactions have been previously shown to increase plasma LH in courting male doves at 24 h, but not at 1 h, after pairing with females. In the first study, males allowed to court females for 2 h had 60% more cells that showed immunocytochemical labeling for GnRH-I in the preoptic area (POA) of the hypothalamus than did control males that remained isolated from females. To determine whether an increase in GnRH gene expression preceded this increase in GnRH immunoreactivity in the POA, changes in the number of cells with detectable GnRH-I mRNA in the POA were measured by in situ hybridization following a 1 h period of courtship interactions with females. In this second study, courting males exhibited 40% more cells with GnRH-I in this region than did isolated control males. GnRH-immunoreactive neurons in two other diencephalic regions failed to show these courtship-induced changes. Plasma LH was not elevated after 1 or 2 h of courtship. These results demonstrate that the release of GnRH-I in the POA that is presumably responsible for courtship-induced pituitary and gonadal activation is accompanied by a rapid increase in GnRH synthesis that occurs before plasma LH levels increase. We suggest that this increase in GnRH synthesis is necessary to support the extended period of HPG axis activation that is seen in this species during the 5-10 day period of courtship and nest building activity.
许多鸟类和哺乳动物的下丘脑 - 垂体 - 性腺（HPG）轴会因繁殖伴侣之间的社交或性互动而发生变化。虽然促性腺激素释放激素（GnRH）神经元活动的改变在刺激这些变化中起重要作用，但尚不清楚GnRH释放的急性行为诱导改变是否伴随着GnRH合成的平行变化。为了研究这种关系，我们检查了雄性环鸽在与雌性进行短暂求偶互动后大脑中GnRH神经元的活动变化。此前已表明，这种互动会使求偶雄性鸽子在与雌性配对后24小时而非1小时时血浆促黄体生成素（LH）增加。在第一项研究中，与雌性进行2小时求偶的雄性鸽子下丘脑视前区（POA）中显示GnRH - I免疫细胞化学标记的细胞比与雌性隔离的对照雄性鸽子多60％。为了确定POA中GnRH基因表达的增加是否先于GnRH免疫反应性的增加，在与雌性进行1小时求偶互动后，通过原位杂交测量POA中可检测到GnRH - I mRNA的细胞数量变化。在第二项研究中，求偶雄性鸽子在该区域中显示GnRH - I的细胞比隔离的对照雄性鸽子多40％。另外两个间脑区域的GnRH免疫反应性神经元未显示出这些求偶诱导的变化。求偶1或2小时后血浆LH未升高。这些结果表明，POA中GnRH - I的释放可能负责求偶诱导的垂体和性腺激活，同时伴随着GnRH合成的快速增加，且这种增加发生在血浆LH水平升高之前。我们认为，GnRH合成的这种增加对于支持该物种在求偶和筑巢活动的5 - 10天期间所见的HPG轴延长激活期是必要的。
