Aste N, Cozzi B, Stankov B, Panzica G
Department of Biochemistry, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192 Japan.
Microsc Res Tech. 2001 Oct 1;55(1):37-47. doi: 10.1002/jemt.1154.
Several data suggest that melatonin may influence avian reproduction by acting at the level of the hypothalamic-hypophisial-gonadal axis, and/or on neural circuits controlling reproductive behaviours. The action of melatonin is exerted through specific receptors whose distribution and pharmacological properties have been extensively investigated. This review will focus on the distribution, sexual dimorphism, and dependence upon the photoperiod of melatonin binding sites in avian species with a special emphasis on Japanese quail. Melatonin receptors are widely distributed in avian brain. They are mostly present in the visual pathways of all the investigated species and in the song controlling nuclei of oscine birds. Sexual dimorphism of melatonin binding sites (higher density in males than in females) was detected in some telencephalic nuclei of songbirds, in the visual pathways, and in the preoptic area of quail. The last region plays a key role in the activation of male quail copulatory behaviour and it hosts a large population of gonadotropin-releasing hormone-containing neurons. Sexual dimorphism of melatonin-binding sites in the above-mentioned regions suggests a differential role for this hormone in the modulation of visual perception, gonadotropin production, and seasonally activated behaviours in male and female quail. Further studies are necessary to understand interrelationships among photic cues, gonadal steroids, density, and sexually dimorphic distribution of melatonin receptors.
多项数据表明，褪黑素可能通过作用于下丘脑 - 垂体 - 性腺轴水平和/或控制生殖行为的神经回路来影响鸟类繁殖。褪黑素的作用是通过其分布和药理学特性已被广泛研究的特定受体来实现的。本综述将重点关注鸟类中褪黑素结合位点的分布、性别二态性以及对光周期的依赖性，特别强调日本鹌鹑。褪黑素受体广泛分布于鸟类大脑中。它们大多存在于所有被研究物种的视觉通路以及鸣禽的鸣叫控制核中。在鸣禽的一些端脑核、视觉通路以及鹌鹑的视前区检测到褪黑素结合位点的性别二态性（雄性密度高于雌性）。最后一个区域在雄性鹌鹑交配行为的激活中起关键作用，并且它含有大量含促性腺激素释放激素的神经元。上述区域中褪黑素结合位点的性别二态性表明该激素在调节雄性和雌性鹌鹑的视觉感知、促性腺激素产生以及季节性激活行为中具有不同作用。有必要进行进一步研究以了解光信号、性腺类固醇、密度和褪黑素受体的性别二态性分布之间的相互关系。
