Yamauchi A, Shizuka F, Yamamoto T, Nikawa T, Kido Y, Rokutan K, Kishi K
Department of Nutrition, School of Medicine, University of Tokushima, Japan.
J Nutr Sci Vitaminol (Tokyo). 1995 Jun;41(3):325-40. doi: 10.3177/jnsv.41.325.
To reveal the role of serotonergic neurons in the regulation of feeding, the levels of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin, in the striatum and the hypothalamus were continuously monitored by an in vivo microdialysis technique. Intake of 20% casein diet did not induce significant changes in the 5-HIAA level in these regions. When rats were fed on 5% casein diet (83.5% carbohydrate diet) for 2 h, the level of 5-HIAA in the striatum gradually increased and reached a maximum (226 +/- 44% of basal level, M +/- SEM, n = 7) at 4 h after stopping the diet. In the medial hypothalamus, its level also increased to 183 +/- 19% (n = 10) at 2 h after starting the diet. On the other hand, a 60% casein diet increased the level of 5-HIAA in the lateral hypothalamus to 138 +/- 19% (n = 10) at 2 h after starting the diet. The intravenous infusion of each of these nutrients, glucose, amino acid mixture or lipid, produced more rapid elevation of the 5-HIAA level than oral intake of the diets. When rats were infused with glucose, its level in the striatum continued to be elevated. In the medial hypothalamus, glucose infusion increased 5-HIAA to the maximum (189 +/- 38%, n = 7) at 4 h after starting infusion. In contrast, serotonergic neurons in the lateral hypothalamus seemed to respond only to infusion of the amino acid mixture, and the level of 5-HIAA reached 163 +/- 14% (n = 5) of the basal level at 1 h after starting the infusion. These results suggest that rapid elevation of glucose or amino acids may independently stimulate serotonin metabolism in these brain areas, participating in the feedback regulation of nutrient intake.
为揭示血清素能神经元在进食调节中的作用，采用体内微透析技术持续监测纹状体和下丘脑中血清素的代谢产物5-羟吲哚乙酸（5-HIAA）的水平。摄入20%酪蛋白饮食并未引起这些区域5-HIAA水平的显著变化。当大鼠喂食5%酪蛋白饮食（83.5%碳水化合物饮食）2小时后，纹状体中5-HIAA水平逐渐升高，并在停止饮食后4小时达到最高值（基础水平的226±44%，M±SEM，n = 7）。在内侧下丘脑，其水平在开始饮食后2小时也升高至183±19%（n = 10）。另一方面，60%酪蛋白饮食在开始饮食后2小时使外侧下丘脑中5-HIAA水平升高至138±19%（n = 10）。静脉输注这些营养素（葡萄糖、氨基酸混合物或脂质）中的任何一种，比口服饮食更快地升高5-HIAA水平。当给大鼠输注葡萄糖时，纹状体中其水平持续升高。在内侧下丘脑，输注葡萄糖在开始输注后4小时使5-HIAA升高至最高值（189±38%，n = 7）。相比之下，外侧下丘脑中的血清素能神经元似乎仅对氨基酸混合物的输注有反应，5-HIAA水平在开始输注后1小时达到基础水平的163±14%（n = 5）。这些结果表明，葡萄糖或氨基酸的快速升高可能独立刺激这些脑区的血清素代谢，参与营养摄入的反馈调节。
