Garau Celia, Aparicio Sara, Rial Rubén V, Nicolau María C, Esteban Susana
Laboratori de Neurofisiologia, Departament de Biologia Fonamental i Ciènces de la Salut, Universitat de les Illes Balears, Ctra. Valldemossa Km 7,5, E-07122 Palma de Mallorca, Spain.
Exp Gerontol. 2006 Apr;41(4):430-8. doi: 10.1016/j.exger.2006.02.003. Epub 2006 Mar 24.
Age related changes in the circadian rhythms and sleep quality has been linked with impairment in the function of the suprachiasmatic nucleus (SCN) and melatonin secretion. The precursor of melatonin, serotonin (5-HT) is a neurotransmitter involved in the synchronisation of the circadian clock located in SCN, which shows decreased levels with age. The present work studied the effects of L-tryptophan, the precursor of 5-HT, on the circadian activity-rest rhythm and c-fos expression in the SCN of young and old ring doves, animals diurnal and monocyclic as humans. Two hours before the onset of dark phase, animals housed in cages equipped for activity recording and maintained under 12/12 L/D conditions, received orally L-tryptophan (100 and 240 mg/kg) and, for comparative purposes, melatonin (2.5 and 5 mg/kg). The administration of both L-tryptophan and melatonin reduced the nocturnal activity of all ring doves although only the highest doses were effective in old ones. A reduced amplitude in the activity-rest rhythm was observed in old animals in comparison to youngest, but it was increased after the treatments. Sleep parameters, calculated from the activity data, indicated a worsened sleep quality in old animals but it was improved with the treatments. In addition, the expression of c-fos in the SCN was reduced after both mentioned treatments. The results point to the SCN as a target for the observed nocturnal effects of L-tryptophan and melatonin, and support the supplemental administration of the essential amino acid L-tryptophan to reverse the disturbances of the circadian activity-rest cycle related with ageing.
昼夜节律和睡眠质量的年龄相关变化与视交叉上核（SCN）功能受损及褪黑素分泌有关。褪黑素的前体血清素（5-HT）是一种神经递质，参与位于SCN的生物钟同步，其水平随年龄增长而降低。本研究探讨了5-HT前体L-色氨酸对青年和老年环鸽SCN中昼夜活动-休息节律和c-fos表达的影响，环鸽与人类一样是昼行性单循环动物。在黑暗期开始前两小时，将饲养在配备活动记录设备的笼子里并维持在12/12光/暗条件下的动物口服L-色氨酸（100和240毫克/千克），并为比较目的给予褪黑素（2.5和5毫克/千克）。L-色氨酸和褪黑素的给药均降低了所有环鸽的夜间活动，尽管只有最高剂量对老年环鸽有效。与最年轻的动物相比，老年动物的活动-休息节律振幅降低，但治疗后有所增加。根据活动数据计算的睡眠参数表明老年动物的睡眠质量较差，但治疗后有所改善。此外，上述两种治疗后SCN中c-fos的表达均降低。结果表明SCN是L-色氨酸和褪黑素夜间作用的靶点，并支持补充必需氨基酸L-色氨酸以逆转与衰老相关的昼夜活动-休息周期紊乱。
