Mess B, Rékási Z, Ghosh M, Csernus V
Department of Anatomy, University Medical School, Pécs, Hungary.
Acta Biol Hung. 1996;47(1-4):313-22.
The melatonin secretory pattern of the perifused rat and chicken pineal was compared in response to different lighting conditions and norepinephrine administration. The following main differences were observed. 1. Explanted (perifused) rat pineal showed, after a rapid initial surge, a steady continuous basal secretion of melatonin. This was independent from the day-night (light-dark) periods. Chicken pineal, however, showed a characteristic daily rhythm of melatonin production with peak in the dark and nadir in the light phase. 2. This daily rhythm could not be extinguished by keeping the pineal donor birds in constant light- or constant dark environment for at least 2 weeks immediately before sacrifice. 3. Short light impulse (5 min), applied in the middle of the dark phase, was ineffective in birds. Keeping the perifusion chambers in continuous light or darkness, however, depressed the amplitude of the circadian rhythm even in the next cycle. 4. Rat pineal responds to norepinephrine stimulation with a dose-related increase of melatonin release, independently from the phase of the day, while in the chicken, norepinephrine slightly inhibits both the diurnal and the nocturnal level of melatonin secretion. 5. It can be inferred that melatonin secretion of the mammalian pineal gland is primarily regulated by a peripheral (sympathetic) innervation. This is modulated, under in vivo circumstances, by different environmental factors, mainly by light conditions transmitted by neural mechanisms. In contrast, the primary secretory process of the avian pineal is based on an intrinsic circadian rhythm. This might be genetically coded or maintained by yet unknown neurohormonal mechanisms and/or external factors (e.g. magnetic fields). This fairly stable circadian rhythm is only modulated by environmental lighting conditions.
比较了在不同光照条件和给予去甲肾上腺素的情况下，灌流大鼠和鸡松果体的褪黑素分泌模式。观察到以下主要差异。1. 移植（灌流）的大鼠松果体在最初快速激增后，呈现褪黑素的稳定持续基础分泌。这与昼夜（明暗）周期无关。然而，鸡松果体显示出褪黑素分泌的特征性日节律，黑暗期达到峰值，光照期降至最低点。2. 在处死前至少2周将松果体供体鸡置于持续光照或持续黑暗环境中，这种日节律不会消失。3. 在黑暗期中间施加短时间光脉冲（5分钟）对鸡无效。然而，将灌流室置于持续光照或黑暗中，即使在下一个周期也会降低昼夜节律的幅度。4. 大鼠松果体对去甲肾上腺素刺激的反应是褪黑素释放量与剂量相关增加，与一天中的阶段无关，而在鸡中，去甲肾上腺素会轻微抑制褪黑素分泌的昼夜水平。5. 可以推断，哺乳动物松果体的褪黑素分泌主要受外周（交感）神经支配调节。在体内情况下，这会受到不同环境因素的调节，主要是通过神经机制传递的光照条件。相比之下，鸟类松果体的主要分泌过程基于内在的昼夜节律。这可能是由基因编码的，或者由未知的神经激素机制和/或外部因素（如磁场）维持。这种相当稳定的昼夜节律仅受环境光照条件的调节。
