Lepage Olivier, Tottmar Olof, Winberg Svante
Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, SE-752 36, Sweden.
J Exp Biol. 2002 Dec;205(Pt 23):3679-87. doi: 10.1242/jeb.205.23.3679.
Juvenile rainbow trout were isolated in individual compartments and allowed to acclimate for 1 week, during which they were fed commercial trout pellets. The feed was then replaced by pelleted feed supplemented with L-tryptophan (TRP) at two, four or eight times the concentration in the commercial feed. Fish were fed these supplemented feeds daily to satiety for 1 week, after which half of the fish were stressed, by lowering the water level for 2 h, while the remaining fish were left undisturbed. In undisturbed fish, supplementary dietary TRP resulted in slightly elevated plasma cortisol levels. In response to the stress, fish that had been fed control feed showed elevated plasma cortisol levels, but fish fed the TRP-supplemented feed displayed a significant reduction in this stress-induced elevation of plasma cortisol levels. Plasma and brain TRP levels were elevated in fish fed TRP-supplemented feed. TRP is the precursor of the monoamine neurotransmitter serotonin. Brain serotonergic activity was elevated by stress and also tended to be increased by elevated dietary TRP intake. The central serotonergic system is involved in the control of the hypothalamic-pituitary-interrenal axis, the action of serotonin being to stimulate or inhibit this neuroendocrine axis through different projections.
将幼年虹鳟鱼隔离在单独的隔间中，使其适应1周，在此期间投喂商业鳟鱼颗粒饲料。然后将饲料换成添加了L-色氨酸（TRP）的颗粒饲料，添加浓度为商业饲料的两倍、四倍或八倍。每天给鱼投喂这些补充饲料直至饱足，持续1周，之后对一半的鱼进行应激处理，即降低水位2小时，而其余的鱼则不做处理。在未受干扰的鱼中，补充膳食TRP会导致血浆皮质醇水平略有升高。对应激的反应中，喂食对照饲料的鱼血浆皮质醇水平升高，但喂食补充TRP饲料的鱼在应激诱导的血浆皮质醇水平升高中有显著降低。喂食补充TRP饲料的鱼血浆和脑内TRP水平升高。TRP是单胺神经递质血清素的前体。应激会提高脑内血清素能活性，膳食TRP摄入量增加也往往会使其升高。中枢血清素能系统参与下丘脑-垂体-肾间轴的调控，血清素通过不同的投射刺激或抑制该神经内分泌轴。
