Míguez J M, Martín F J, Aldegunde M
Laboratorio de Fisioloxia Animal, Facultade de Bioloxia, Universidade de Santiago de Compostela, Spain.
Neurochem Res. 1997 Jan;22(1):87-92. doi: 10.1023/a:1027337606929.
This work examined the influence of the pineal gland and its hormone melatonin on the metabolism of serotonin (5-HT) in discrete areas of the forebrain, such as the striatum and the nucleus accumbens, and the midbrain raphe. The content of 5-HT and its major oxidative metabolite, the 5-hydroxyindoleacetic acid (5-HIAA), as well as the in-vivo tryptophan hydroxylation rate were examined after long-term pinealectomy (one month) and daily melatonin treatment (500 micrograms/kg; twice daily for ten days) in pinealectomized rats. Pinealectomy did not alter 5-HT content in any of these brain areas, but it significantly increased the content of 5-HIAA in striatum and the 5-HIAA/5-HT ratio in nucleus accumbens. The normal values of these parameters were recuperated after administration of exogenous melatonin, but it also increased the rate of tryptophan hydroxylation in both areas. In addition, melatonin treatment decreased the levels of 5-HIAA in dorsal raphe nucleus. These data suggest that the pineal gland, through the secretion of melatonin, modulates the local metabolism of 5-HT in forebrain areas by acting on the oxidative deamination. Moreover, melatonin injected in pinealectomized rats derives in a more extended effect than pinealectomy and induces a stimulation of 5-HT synthesis in the striatum, probably due to a pharmacological effect. These results point to the striatum as a target area for the interaction between pineal melatonin and the serotonergic function, and suggest a differential effect of the melatonin injected on areas containing serotonergic terminals and cell bodies, which may relevant for the mode of action of melatonin and its behavioral effects.
这项研究探讨了松果体及其激素褪黑素对前脑离散区域（如纹状体和伏隔核）以及中脑缝际中血清素（5-羟色胺，5-HT）代谢的影响。在长期松果体切除（一个月）以及对松果体切除的大鼠进行每日褪黑素治疗（500微克/千克；每日两次，持续十天）后，检测了5-HT及其主要氧化代谢产物5-羟吲哚乙酸（5-HIAA）的含量，以及体内色氨酸羟化率。松果体切除并未改变这些脑区中任何一个的5-HT含量，但显著增加了纹状体中5-HIAA的含量以及伏隔核中5-HIAA/5-HT的比值。给予外源性褪黑素后，这些参数的正常值得以恢复，但同时也提高了这两个区域的色氨酸羟化率。此外，褪黑素治疗降低了背侧缝际核中5-HIAA的水平。这些数据表明，松果体通过分泌褪黑素，作用于氧化脱氨基过程，从而调节前脑区域5-HT的局部代谢。而且，给松果体切除的大鼠注射褪黑素产生的作用比松果体切除更广泛，并诱导纹状体中5-HT合成增加，这可能是由于药理作用。这些结果表明纹状体是松果体褪黑素与5-羟色胺能功能相互作用的靶区域，并提示注射的褪黑素对含有5-羟色胺能终末和细胞体的区域具有不同的作用，这可能与褪黑素的作用方式及其行为效应相关。
