Table_5_Photoperiodic Changes in Both Hypothalamus Neurotransmitters and Circulating Gonadal Steroids Metabolomic Profiles in Relation to Seasonal Reproduction in Male Quail.docx

Both hypothalamic neurotransmitters and serum steroid hormones are impacted by photoperiod and have effects on physiology and seasonal reproductive. However, the relationship between circulating gonadal steroids and hypothalamic neurotransmitters underlying different photoperiod is still unclear. To further understand the crosstalk of neurotransmitters and steroids in seasonal reproduction, metabolic changes of 27 neurotransmitters concentrated in hypothalamus tissues and 42 steroids hormones in serum were assessed during two artificial photoperiodic programs. The results showed that photoperiod induce testicular atrophy and recrudescence. In L-to-S groups, significantly decreased levels of testosterone concentration were found in serum (P < 0.001) and increased 11-Dehydrocorticosterone (P < 0.05); Testosterone were almost undetectable at SD_14d. In addition, the hypothalamus exhibited significantly increased arginine and 4-aminobutyric acid (GABA) concentration and decreased serotonin and epinephrine content (P < 0.01 or P < 0.05). Accordingly, serum testosterone and androstenedione became detectable at LD_3d in the S-to-L group and were markedly increase at LD_7d. Furthermore, Serum androstenedione showed a significant increase with long light expose (P < 0.01). Additionally, the hypothalamus exhibited both significantly increased L.Tryptophan and phenylalanine concentration, as well as decreased L-glutamine and L-glutamine.acid content (P < 0.01 or P < 0.05). Serotonin metabolism showed significant differences between L-to-S group and S-to-L group. Furthermore, in the correlation analysis, serum testosterone had a positive correlation with 5-Hydroxyindole-3-acetic acid (5-HIAA), while Androstenedione was significantly negative with L.Tryptophan in L-to-S (P < 0.05). However, in S-to-L group, serum testosterone showed strong negative correlation with both serotonin and 5-HIAA (P < 0.05), but positive correlation with L.Tryptophan (P < 0.01), while Androstenedione was significantly negative correlation with both serotonin (P < 0.05) and L-Glutamine (P < 0.01). Photoperiod also had significant effects on the mRNA expression. We found significant differences in gene expression patterns of both serotonin signaling and steroid biosynthesis, while MAOB, NR5A1, and 3β-HSD showed an opposite tendency between two groups. Taken together, our results revealed that circulating gonadal steroids and hypothalamic neurotransmitters were significantly impact quail’s seasonal reproduction. Circulating gonadal steroids have different effects on neurotransmitter at different photoperiodism, which may coordinately influence the seasonal reproduction of quails.

下丘脑神经递质与血清类固醇激素均受光周期（photoperiod）调控，并对生理活动及季节性生殖过程产生影响。然而，不同光周期条件下，循环性腺类固醇激素与下丘脑神经递质之间的互作调控机制仍未明确。为进一步阐明季节性生殖过程中神经递质与类固醇激素的互作调控网络，本研究针对两种人工光周期处理方案下，下丘脑组织中富集的27种神经递质以及血清中42种类固醇激素的代谢变化展开了检测分析。
研究结果显示，光周期可诱导睾丸发生萎缩与复发育。在长光照转短光照（Long-to-Short, L-to-S）组中，血清睾酮水平显著降低（P < 0.001），而11-脱氢皮质酮（11-Dehydrocorticosterone）水平显著升高（P < 0.05）；在短光照第14天（SD_14d）时，睾酮水平几乎无法被检测到。此外，下丘脑组织中的精氨酸与γ-氨基丁酸（4-aminobutyric acid, GABA）浓度显著升高，而5-羟色胺与肾上腺素含量则显著降低（P < 0.01 或 P < 0.05）。
相应地，在短光照转长光照（Short-to-Long, S-to-L）组中，血清睾酮与雄烯二酮在长光照第3天（LD_3d）即可被检测到，并在长光照第7天（LD_7d）时显著升高。此外，随着长光照暴露时长增加，血清雄烯二酮水平呈现显著上升趋势（P < 0.01）。同时，下丘脑组织中的L-色氨酸（L-Tryptophan）与苯丙氨酸浓度显著升高，而L-谷氨酰胺与L-谷氨酸含量则显著降低（P < 0.01 或 P < 0.05）。
5-羟色胺代谢通路在长光照转短光照组与短光照转长光照组间存在显著差异。进一步的相关性分析显示，在长光照转短光照组中，血清睾酮与5-羟吲哚乙酸（5-Hydroxyindole-3-acetic acid, 5-HIAA）呈正相关，而雄烯二酮与L-色氨酸呈显著负相关（P < 0.05）。而在短光照转长光照组中，血清睾酮与5-羟色胺及5-羟吲哚乙酸均呈显著负相关（P < 0.05），但与L-色氨酸呈正相关（P < 0.01）；雄烯二酮则与5-羟色胺（P < 0.05）及L-谷氨酰胺（P < 0.01）均呈显著负相关。
光周期对mRNA表达水平同样存在显著影响。本研究发现，5-羟色胺信号通路与类固醇生物合成通路的基因表达模式均存在显著差异，且单胺氧化酶B（MAOB）、核受体亚家族5A组1成员（NR5A1）及3β-羟类固醇脱氢酶（3β-HSD）在两组间的表达趋势恰好相反。
综合来看，本研究结果表明，循环性腺类固醇激素与下丘脑神经递质均对鹌鹑的季节性生殖过程产生显著调控作用；不同光周期条件下，循环性腺类固醇激素对神经递质的调控作用存在差异，二者可能协同影响鹌鹑的季节性生殖活动。