Peripheral factors associated with early response in feeding to lysine-free diet in growing chickens

本研究的目的是确定哪些外周因素与无赖氨酸日粮鸡的早期摄食量减少有关，以及这些因素的变化通过何种途径传递到中枢神经系统。实验日粮为纯化对照（赖氨酸。HCL 11.9 g/kg）和无赖氨酸（无赖氨酸。无赖氨酸日粮饲喂后1小时，血浆赖氨酸浓度开始下降，仅为对照组的三分之一，并持续下降至第4小时。除赖氨酸外的其他氨基酸均不随日粮赖氨酸水平变化。无赖氨酸饮食的鸡的食物摄入量在饮食呈现后5或6小时开始减少。这一结果表明，血浆中游离氨基酸的浓度触发了对无赖氨酸饮食的摄食反应。在梨状前皮质或下丘脑中，已知参与摄食调节的游离氨基酸浓度在喂食无赖氨酸饮食后下降了对照的一半，但在皮质中观察到类似的变化。延髓Fos免疫组化结果显示，在喂食后3 h，去赖氨酸组孤束核（NTS）Fos免疫反应阳性细胞数明显多于对照组。2 h后，去赖氨酸组大鼠中脑腹外侧核（Ac）出现Fos阳性细胞。这些结果表明，外周信息的血浆中的氨基酸浓度传达通过NTS，并得到了Ac。总之，早期减少食物摄入量的鸡无赖氨酸饮食发生后，在血浆中的赖氨酸浓度的变化，通过NTS传达，并得到了Ac。

The objective of this project was to determine what peripheral factors were related to early reduction in food intake by chickens on lysine-free diet and which way conveyed the change of factors to the central nervous system.Three week-old male layer-type chickens were used. Experimental diets were purified-control (lysine. HCL11.9 g/kg) and lysine-free (no lysine. HCL) diets with same nitrogen and ME content.One hour after the lysine-free diet were presented, plasma concentration of lysine started to decrease to third of the control, and continued to decrease up to the fourth hours. Other amino acids than lysine did not change with dietary lysine level. Food intake by chickens on lysine-free diet started to decrease 5 or 6 hours after the diet was presented. This result suggests that plasma concentration of free amino acids triggered the response of feeding to lysine-free diet. Free amino acids concentration ini the pre-piriform cortex or hypothalamus, which was known to be involved in regulation of feeding, after feeding the lysine-free diet decreased half of the control, but similar changes were observed in the cortex. Therefore, tit is unlikely that amino acid in the brain did not relate to the response.Fos immunohistochemistry with medulla oblongata shows that the number of Fos immunoreactive cells observed at nucleus tractus solitarius(NTS) was larger in the lysine-free than control groups at three hours after presenting the diet. Two hours later Fos immunoreactive cells appeared at the nucleus accumbens (Ac) in the lysine-free group. These results suggest that peripheral information of plasma concentration of amino acid was conveyed thorough the NTS and got to the Ac.In conclusion, early reduction of food intake by chickens on lysine-free diet occurs after change in plasma concentration of lysine that is conveyed through the NTS and gets to the Ac.