Laakso M L, Alila A, Hätönen T, Mustanoja S M
Department of Physiology, University of Helsinki, Finland.
J Pineal Res. 1996 Oct;21(3):155-64. doi: 10.1111/j.1600-079x.1996.tb00283.x.
The aim of the study was to determine whether a discrepancy between the genetically determined endogenous circadian period and an abnormally long Zeitgeber period disturbs the development of melatonin synthesis. Breeding pairs of rats were kept under 12:12- or 14:14-hr light:dark (LD) conditions. Pineal melatonin contents in the offspring were measured by radioimmunoassay. At 2 weeks of age high melatonin contents were found from lights-off to lights-on in both conditions suggesting dominance of the photic regulation. At 3 weeks of age the signs of the circadian regulation in the melatonin profiles were evident: a lag period after the light offset in control conditions and a significant decline before the light onset in both conditions. However, in 14:14-hr LD conditions the melatonin content did not decrease to daytime levels until the lights were on. This could suggest incomplete maturation of the circadian system. The phase relationships between the melatonin peak and LD cycle were different in the two conditions. A statistically significant LD difference was first found at the age of 8-10 days in male pups and at 14 days in female pups under both lighting. The results suggest that the abnormally long LD cycle did not cause any major disorders in the development of photic or circadian regulation of the melatonin synthesis.
本研究的目的是确定基因决定的内源性昼夜节律周期与异常长的昼夜节律周期之间的差异是否会干扰褪黑素合成的发育。将繁殖对大鼠置于12:12或14:14小时光照:黑暗（LD）条件下。通过放射免疫测定法测量后代松果体中的褪黑素含量。在2周龄时，在两种条件下均发现从熄灯到开灯期间褪黑素含量较高，这表明光调节占主导地位。在3周龄时，褪黑素谱中的昼夜节律调节迹象明显：在对照条件下，光照结束后有一个延迟期，在两种条件下光照开始前均有显著下降。然而，在14:14小时LD条件下，直到开灯时褪黑素含量才降至白天水平。这可能表明昼夜节律系统发育不完全成熟。在两种条件下，褪黑素峰值与LD周期之间的相位关系不同。在两种光照条件下，雄性幼崽在8 - 10天龄时首次发现统计学上显著的LD差异，雌性幼崽在14天龄时首次发现。结果表明，异常长的LD周期在褪黑素合成的光调节或昼夜节律调节发育过程中未引起任何重大紊乱。
