Meissl H, Kroeber S, Yáñez J, Korf H W
Max-Planck-Institute for Physiological and Clinical Research, W.G. Kerckhoff-Institute, Parkstrasse 1, D-61231 Bad Nauheim, Germany.
Cell Tissue Res. 1996 Dec;286(3):315-23. doi: 10.1007/s004410050701.
The present in vitro study correlates measurements of the melatonin production from trout pineal organs with those of the intracellular calcium concentration in pinealocytes. Melatonin production increases with decreasing irradiance and shows maximal values in darkness. Some pinealocytes exhibit spontaneous calcium oscillations, although most of them have a stable basal calcium concentration. Diminishing extracellular calcium and enhancing magnesium reduces melatonin release in the light-and dark-adapted state. The application of Co2+ decreases melatonin secretion in the mesopic and scotopic range, reversibly blocks spontaneous calcium oscillations, reduces the basal intracellular calcium concentration in non-oscillating pinealocytes, and inhibits the KCl-induced rise in intracellular calcium. Application of glutamate, norepinephrine, isoproterenol, or dopamine has no significant effect on melatonin secretion. Norepinephrine does not influence the calcium concentration in any of the trout pinealocytes. Treatment with the GABAA-receptor agonist muscimol causes a slight reduction of melatonin release in the mesopic and scotopic range of illumination, without affecting intracellular calcium concentrations. Thus, Co2+ and low calcium/high magnesium buffer reduce melatonin release through an action on the calcium concentration in trout pinealocytes and not through a blockade of synaptic transmission. All the data show that the trout pineal organ synthesizes and releases melatonin in relation to the irradiance of the incident light and that neuronal inputs have a minor, if any, influence on melatonin synthesis.
本体外研究将虹鳟松果体器官褪黑素生成的测量结果与松果体细胞内钙浓度的测量结果相关联。褪黑素生成随光照强度降低而增加，在黑暗中达到最大值。一些松果体细胞表现出自发性钙振荡，尽管大多数细胞具有稳定的基础钙浓度。降低细胞外钙浓度并增加镁浓度会减少适应光照和黑暗状态下的褪黑素释放。Co2+的应用在中暗视觉范围内降低褪黑素分泌，可逆地阻断自发性钙振荡，降低非振荡性松果体细胞的基础细胞内钙浓度，并抑制KCl诱导的细胞内钙升高。谷氨酸、去甲肾上腺素、异丙肾上腺素或多巴胺的应用对褪黑素分泌无显著影响。去甲肾上腺素不影响任何虹鳟松果体细胞中的钙浓度。用GABAA受体激动剂蝇蕈醇处理会在中暗视觉光照范围内使褪黑素释放略有减少，但不影响细胞内钙浓度。因此，Co2+和低钙/高镁缓冲液通过作用于虹鳟松果体细胞中的钙浓度来减少褪黑素释放，而不是通过阻断突触传递。所有数据表明，虹鳟松果体器官根据入射光的光照强度合成并释放褪黑素，并且神经元输入对褪黑素合成的影响很小（如果有影响的话）。
