Hasegawa Shu, Kanemaru Kazuya, Gittos Maurice, Diksic Mirko
Cone Neurosurgical Research Laboratory, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Que., Canada H3A 2B4.
Brain Res Bull. 2005 Oct 15;67(3):248-55. doi: 10.1016/j.brainresbull.2005.07.009.
Many experimental conditions are stressful for animals. It is well known that stress induces tryptophan hydroxylase (TPH) activation, resulting in increased serotonin (5-HT) synthesis. In our experimental procedure to measure 5-HT synthesis using alpha-[(14)C]methyl-L-tryptophan (alpha-MTrp) autoradiographic method, the hind limbs of animals are restrained using a loose-fitted plaster cast such that the forelimbs of the animal remain free. The objective of the present investigation was to evaluate the changes, if any, in 5-HT synthesis, after injecting these restrained rats with the TPH activation inhibitor AGN-2979. The effect on regional 5-HT synthesis was studied using the alpha-MTrp autoradiographic method. The hypothesis was that the TPH activation inhibitor would reduce 5-HT synthesis, if TPH activation was induced by this restraint. The rats received injection of AGN-2979 (10 mg/kg, i.p.) or distilled water vehicle (1 mL/kg, i.p.) 1 h prior to tracer administration. The free- and total tryptophan concentrations were not significantly different between the treatment and control groups. The results demonstrate that 5-HT synthesis in AGN-2979 treated rats is significantly decreased (-12 to -35%) in both the raphe nuclei and their terminal areas when compared to the control rats. These findings suggest that restrained conditions, such as those used in our experimental protocol, induce TPH activation resulting in an increased 5-HT synthesis throughout the brain. The reduction in 5-HT synthesis in the AGN-2979 group is not related to a change in the plasma tryptophan. Because there was no activation in the pineal body, the structure having a different isoform of TPH, we can propose that it is only the brain TPH that becomes activated with this specific restraint.
许多实验条件对动物来说都具有压力。众所周知，压力会诱导色氨酸羟化酶（TPH）激活，从而导致血清素（5-HT）合成增加。在我们使用α-[(14)C]甲基-L-色氨酸（α-MTrp）放射自显影法测量5-HT合成的实验过程中，用宽松的石膏绷带固定动物的后肢，使动物的前肢保持自由。本研究的目的是评估给这些受约束的大鼠注射TPH激活抑制剂AGN-2979后5-HT合成是否有变化。使用α-MTrp放射自显影法研究对局部5-HT合成的影响。假设是，如果这种约束诱导了TPH激活，那么TPH激活抑制剂将减少5-HT合成。在给予示踪剂前1小时，大鼠接受AGN-2979（10mg/kg，腹腔注射）或蒸馏水载体（1mL/kg，腹腔注射）。治疗组和对照组之间的游离色氨酸和总色氨酸浓度没有显著差异。结果表明，与对照大鼠相比，AGN-2979处理的大鼠中缝核及其终末区域的5-HT合成显著降低（-12%至-35%）。这些发现表明，如我们实验方案中所使用的约束条件会诱导TPH激活，导致全脑5-HT合成增加。AGN-2979组中5-HT合成的减少与血浆色氨酸的变化无关。由于松果体（具有不同TPH同工型的结构）没有激活，我们可以提出，只有脑TPH会因这种特定的约束而被激活。
