Mennigen Jan A, Volkoff Hélène, Chang John P, Trudeau Vance L
Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada; Department of Biochemistry, Memorial University of Newfoundland, St John's, NL, Canada.
Gen Comp Endocrinol. 2017 Dec 1;254:38-49. doi: 10.1016/j.ygcen.2017.09.008. Epub 2017 Sep 18.
Nonapeptides are a highly conserved family of peptides synthesized in the neuroendocrine brain and acting on central and peripheral receptors to regulate physiological functions in vertebrates. While the evolution of the two gene families of oxytocin-like and vasopressin-like nonapeptides and their receptors, as well as the neuroanatomy of their independent neuronal circuits have been well-characterized across vertebrate species, comparative studies on the physiological roles across vertebrates are lagging behind. In the current study, we focused on the comparative neuroendocrine functions and regulation of isotocin, the teleost homologue of mammalian oxytocin. Specifically, we address the hypothesis that isotocin exerts opposing effects on food intake and reproduction, which are well-established effects of its homologue oxytocin in mammalian species. Using goldfish, a well-characterized model of neuroendocrine regulation of both food intake and reproduction, we here showed that isotocin acts as an anorexigenic factor while exerting stimulatory effects on pituitary luteinizing hormone and growth hormone release. Given the dual inhibitory and stimulatory roles of serotonin on food intake and pituitary release of reproductive hormone in goldfish, we also investigated the potential crosstalk between both systems using immunohistochemistry and pharmacological approaches. Results provide neuroanatomical and pharmacological evidence for serotonergic regulation of magnocellular isotocinergic neurons in the preoptic area and pituitary. Together, these findings firstly provide the basis to investigate neuroendocrine cross-talk between serotonergic and nonapeptidergic systems in the regulation of both food intake and reproduction in goldfish, and secondly point to a conserved function of oxytocin-like peptides in the differential neuroendocrine control of both physiological processes in vertebrates.
九肽是一类高度保守的肽家族，在神经内分泌脑区合成，作用于中枢和外周受体，以调节脊椎动物的生理功能。虽然催产素样和加压素样九肽及其受体的两个基因家族的进化，以及它们独立神经回路的神经解剖学在整个脊椎动物物种中已得到充分表征，但关于脊椎动物生理作用的比较研究却滞后了。在当前的研究中，我们聚焦于硬骨鱼催产素（哺乳动物催产素的硬骨鱼同源物）的比较神经内分泌功能及其调节。具体而言，我们探讨了这样一个假设，即硬骨鱼催产素对食物摄入和繁殖产生相反的影响，而其同源物催产素在哺乳动物物种中对这些方面的影响已得到充分证实。利用金鱼这一在食物摄入和繁殖的神经内分泌调节方面特征明确的模型，我们在此表明，硬骨鱼催产素作为一种厌食因子，同时对垂体促黄体生成素和生长激素的释放具有刺激作用。鉴于血清素在金鱼食物摄入和垂体生殖激素释放方面具有双重抑制和刺激作用，我们还使用免疫组织化学和药理学方法研究了这两个系统之间潜在的相互作用。结果为视前区和垂体中血清素能对大细胞硬骨鱼催产素能神经元的调节提供了神经解剖学和药理学证据。总之，这些发现首先为研究血清素能和九肽能系统在金鱼食物摄入和繁殖调节中的神经内分泌相互作用提供了基础，其次指出了催产素样肽在脊椎动物这两个生理过程的差异神经内分泌控制中的保守功能。
