Melatonin sees the light: blocking GABA-ergic transmission in the paraventricular nucleus induces daytime secretion of melatonin
Melatonin sees the light: blocking GABA-ergic transmission in the paraventricular nucleus induces daytime secretion of melatonin
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DOI：
10.1046/j.1460-9568.2000.00202.x
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发表时间：
2000-09-01
影响因子：
3.4
通讯作者：
Buijs, RM
中科院分区：
文献类型：
--
作者：
Kalsbeek, A;Garidou, ML;Buijs, RM
尽管光对松果体褪黑激素的合成有明显的抑制作用，但通常褪黑激素的每日节律并不是对周围世界的被动反应。在哺乳动物中，以及迄今为止研究的几乎所有其他脊椎动物物种中，褪黑激素节律与内源性起搏器（即昼夜节律钟）耦合。在哺乳动物中，主要的昼夜节律起搏点位于视交叉上核（SCN），这是下丘脑前部的一个双侧神经元簇。在本文中，我们表明，在大鼠中，双边取消γ-氨基丁酸（GABA），但不是加压素，在SCN的目标区域，即下丘脑室旁核的神经传递，在（主观）白天的结果增加松果体褪黑激素水平。SCN的完全去除导致白天松果体芳烷基胺N-乙酰基转移酶（AA-NAT），即褪黑激素合成的限速酶的mRNA水平显著增加的事实，进一步证实了存在控制昼夜褪黑激素节律的主要抑制性SCN输出。
Despite a pronounced inhibitory effect of light on pineal melatonin synthesis, usually the daily melatonin rhythm is not a passive response to the surrounding world. In mammals, and almost every other vertebrate species studied so far, the melatonin rhythm is coupled to an endogenous pacemaker, i.e. a circadian clock. In mammals the principal circadian pacemaker is located in the suprachiasmatic nuclei (SCN), a bilateral cluster of neurons in the anterior hypothalamus. In the present paper we show in the rat that bilateral abolition of gamma-aminobutyric acid (GABA), but not vasopressin, neurotransmission in an SCN target area, i.e. the paraventricular nucleus of the hypothalamus, during (subjective) daytime results in increased pineal melatonin levels. The fact that complete removal of the SCN results in a pronounced increase of daytime pineal mRNA levels for arylalkylamine N-acetyltransferase (AA-NAT), i.e. the rate-limiting enzyme of melatonin synthesis, further substantiates the existence of a major inhibitory SCN output controlling the circadian melatonin rhythm.