Currie P J, Chang N, Luo S, Anderson G H
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, ON, Canada.
Life Sci. 1995;57(21):1911-23. doi: 10.1016/0024-3205(95)02178-l.
Regional and dietary-induced changes in hypothalamic extracellular amino acid concentrations were examined. Microdialysis probes were simultaneously implanted in the hypothalamic paraventricular nucleus (PVN) and the lateral hypothalamus (LH) of anesthetized rats and perfused at a rate of 2 microliters/min. Dialysates were collected every 20 min for 1 h prior to gavage of a balanced amino acid mixture (0.85 g patterned after 1 g of chicken egg albumin) and then every 20 min for 3 h after treatment. Tail vein blood samples were also collected. Marked changes in plasma levels of most amino acids were evident immediately following the amino acid gavage. In the PVN, concentrations of isoleucine, leucine, methionine and valine all increased within 40 min, whereas significant decreases in glutamine, histidine and taurine were observed in the LH. In a separate study, PVN extracellular amino acid concentrations were examined in awake, freely-behaving rats following gavage of equicaloric loads of a balanced amino acid mixture, glucose (0.89 g) or water. Dialysate levels of glutamate, isoleucine, leucine, methionine, threonine, tyrosine and valine showed reliable increases after amino acid treatment, although the overall time course of these effects differed somewhat. The amino acid profile of the PVN was, in general, unaffected by glucose administration. These findings suggest that specific brain regions may respond uniquely to amino acid ingestion and further imply that dietary composition may influence the amino acid profiles of the extracellular fluid in brain.
研究了下丘脑细胞外氨基酸浓度的区域和饮食诱导变化。将微透析探针同时植入麻醉大鼠的下丘脑室旁核（PVN）和外侧下丘脑（LH），并以2微升/分钟的速率进行灌注。在灌胃平衡氨基酸混合物（0.85克，仿照1克鸡蛋白白蛋白配制）前1小时，每20分钟收集一次透析液，共收集1小时，然后在处理后每20分钟收集一次透析液，共收集3小时。同时采集尾静脉血样。氨基酸灌胃后，大多数氨基酸的血浆水平立即出现明显变化。在PVN中，异亮氨酸、亮氨酸、蛋氨酸和缬氨酸的浓度在40分钟内均升高，而在LH中观察到谷氨酰胺、组氨酸和牛磺酸显著降低。在另一项研究中，对清醒、自由活动的大鼠灌胃等热量的平衡氨基酸混合物、葡萄糖（0.89克）或水后，检测PVN细胞外氨基酸浓度。氨基酸处理后，谷氨酸、异亮氨酸、亮氨酸、蛋氨酸、苏氨酸、酪氨酸和缬氨酸的透析液水平显示出可靠的升高，尽管这些效应的总体时间进程略有不同。一般来说，PVN的氨基酸谱不受葡萄糖给药的影响。这些发现表明，特定脑区可能对氨基酸摄入有独特反应，并进一步暗示饮食组成可能影响脑内细胞外液的氨基酸谱。
