Thibault C, Falcón J, Greenhouse S S, Lowery C A, Gern W A, Collin J P
Laboratoire de Neurobiologie et Neuroendocrinologie Cellularies, URA CNRS 290, Faculté des Sciences, Université de Poitiers, France.
J Neurochem. 1993 Jul;61(1):332-9. doi: 10.1111/j.1471-4159.1993.tb03572.x.
The light/dark cycle influences the rhythmic production of melatonin by the trout pineal organ through a modulation of the serotonin N-acetyltransferase (NAT) activity. In static organ culture, cyclic AMP (cAMP) levels (in darkness) and NAT activity (in darkness or light) were stimulated in the presence of forskolin, isobutylmethylxanthine, or theophylline. Analogues of cAMP, but not of cyclic GMP, induced an increase in NAT activity. Light, applied after dark adaptation, inhibited NAT activity. This inhibitory effect was partially prevented in the presence of drugs stimulating cAMP accumulation. In addition, cAMP accumulation and NAT activity increase, induced by forskolin, were temperature dependent. Finally, melatonin release, determined in superfused organs under normal conditions of illumination, was stimulated during the light period of a light/dark cycle by adding an analogue of cAMP or a phosphodiesterase inhibitor. However, no further increase in melatonin release was observed during the dark phase of this cycle in the presence of the drugs. This report shows for the first time that cAMP is a candidate as intracellular second messenger participating in the control of NAT activity and melatonin production by light and temperature.
光/暗周期通过调节血清素N-乙酰基转移酶（NAT）的活性，影响虹鳟松果体器官褪黑素的节律性分泌。在静态器官培养中，福斯可林、异丁基甲基黄嘌呤或茶碱存在时，（黑暗条件下的）环磷酸腺苷（cAMP）水平和（黑暗或光照条件下的）NAT活性均受到刺激。cAMP类似物而非环磷酸鸟苷（cGMP）类似物可诱导NAT活性增加。暗适应后施加光照会抑制NAT活性。在刺激cAMP积累的药物存在时，这种抑制作用会部分受到阻止。此外，福斯可林诱导的cAMP积累和NAT活性增加与温度有关。最后，在正常光照条件下的灌流器官中测定的褪黑素释放，在光/暗周期的光照期通过添加cAMP类似物或磷酸二酯酶抑制剂受到刺激。然而，在该周期的黑暗期，在药物存在的情况下未观察到褪黑素释放的进一步增加。本报告首次表明，cAMP作为细胞内第二信使，参与了光和温度对NAT活性及褪黑素分泌的调控。
