Phansuwan-Pujito P, Møller M, Govitrapong P
Department of Anatomy, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand.
Microsc Res Tech. 1999;46(4-5):281-95. doi: 10.1002/(SICI)1097-0029(19990815/01)46:4/5<281::AID-JEMT5>3.0.CO;2-N.
Besides the noradrenergic sympathetic system originating from the superior cervical ganglion, a cholinergic innervation of the mammalian pineal gland has been studied over the past three decades. In 1961, it was shown that lesion of the parasympathetic greater superficial petrosal nerve of the monkey resulted in degeneration of nerve fibers in the pineal gland. This was supported by ultrastructural studies of nerve terminals within the pineal gland, demonstrating the presence of cholinergic terminals containing small clear transmitter vesicles. Biochemical studies further showed the presence of the enzyme acetylcholinesterase in several mammalian species. During the last decade, several advanced and more elaborate technologies have been developed, allowing pinealogists to establish the presence of cholinergic fibers and their receptors. Thus, choline acetyltransferase was shown in bovine pineal by immunohistochemistry. Muscarinic and nicotinic receptors were identified, characterized, and localized. Gene expression of receptors was visualized, and the receptor-mediated effector systems and functions were elucidated. Taken together, the present data suggest the presence of a cholinergic innervation of the mammalian pineal gland originating in peripheral parasympathetic ganglia. However, some of the neuronal projections to the pineal gland with origin in the brain (the central innervation) might also be cholinergic. The cholinergic nerve fibers enter the gland, where they are located both in the perivascular spaces and between the pinealocytes. Some of the terminals make synapses on pinealocytes or intrapineal neurons. The released acetylcholine from the terminals interacts with the receptors, then alters the cascade of receptor-mediated events, which results in decreased N-acetyltransferase enzyme activity, thus leading to decreased melatonin synthesis. This counterbalance mechanism between the sympathetic noradrenergic and the cholinergic systems maintains the homeostasis of pineal functions.
除了源自颈上神经节的去甲肾上腺素能交感神经系统外，在过去三十年中，人们对哺乳动物松果体的胆碱能神经支配进行了研究。1961年，研究表明，猴子的副交感神经岩浅大神经受损会导致松果体中的神经纤维退化。松果体内神经末梢的超微结构研究支持了这一观点，该研究表明存在含有小而清亮递质囊泡的胆碱能末梢。生化研究进一步表明，在几种哺乳动物中存在乙酰胆碱酯酶。在过去十年中，人们开发了几种先进且更精细的技术，使松果体研究人员能够确定胆碱能纤维及其受体的存在。因此，通过免疫组织化学在牛松果体中显示了胆碱乙酰转移酶。鉴定、表征并定位了毒蕈碱受体和烟碱受体。可视化了受体的基因表达，并阐明了受体介导的效应系统和功能。综上所述，目前的数据表明哺乳动物松果体存在起源于外周副交感神经节的胆碱能神经支配。然而，一些起源于大脑（中枢神经支配）并投射到松果体的神经元也可能是胆碱能的。胆碱能神经纤维进入腺体，它们位于血管周围间隙和松果体细胞之间。一些末梢与松果体细胞或松果体内神经元形成突触。末梢释放的乙酰胆碱与受体相互作用，然后改变受体介导的一系列事件，导致N - 乙酰转移酶活性降低，从而导致褪黑素合成减少。交感去甲肾上腺素能系统和胆碱能系统之间的这种平衡机制维持了松果体功能的稳态。
