Neural mechanism and relationship between cutaneous active vasodilation and sweating and the role of vasodilative peptides and nitric oxide

在人类的一般皮肤表面，皮肤血管扩张伴随着热出汗。为了阐明其关系和神经机制，我们研究了尼古丁和乙酰胆碱给药后前臂皮肤的出汗和皮肤血流反应。轴突反射介导的出汗和皮肤血流的平行性表明轴突反射出汗也伴有皮肤血管舒张。阿托品能消除出汗，但不能消除皮肤血管舒张，表明血管舒张不是由毒蕈碱受体介导的。在猫爪出汗模型中，血管舒张伴随着出汗，与人类相同。众所周知，乙酰胆碱是人体出汗的主要介质，通过内皮细胞产生NO（一氧化氮）诱导血管舒张。强烈期望NO参与热出汗。由于已知VIP、CGRP和ANP等血管舒张肽存在于汗腺周围，NO可能通过这些肽作用于皮肤血管和汗腺。一氧化氮介导的出汗与皮肤血管舒张的联动机制有待于进一步的研究揭示。这两项应用QSART （Quantitative Sudomotor Axone Reflex Test，定量Sudomotor Axone反射测试）的研究表明，热带居民的耐热性至少在某些部分是通过出生后长期居住在热带环境中获得的，并且男性的前臂汗腺数量较多，单个汗腺的排汗量也较大，这两者都有助于男性的耐热性优于女性。在这些方法的结合下，热出汗和活跃的皮肤血管舒张的相互关系的机制研究将会加强。

On the general skin surface of the humans, cutaneous vasodilation is accompanied by thermal sweating. To elucidate its relationship and neural mechanisms, we studied sweating and skin blood flow responses after administration of nicotine and acetylcholine to the forearm skin. Parallelism of the axone reflex-mediated sweating and skin blood flow indicated that axone reflex sweating is also accompanied by cutaneous vasodilation. Abolishment of sweating but not of cutaneous vasodilation by atropine indicated that vasodilation is mediated by other than muscarinic receptor. In the cat paw sweating model, vasodilation was accompanied by sweating as same as in humans. It is known that acetylcholine, a primary mediator of human sweating, induced vasodilation through NO (nitric oxide) production from the endothelium. Involvement of NO on thermal sweating is strongly expected. Since the vasodilative peptides such as VIP, CGRP and ANP are known to exist around the sweat glands, NO may act on the skin vessels and sweat glands through these peptides. NO-mediated linkage of mechanism of sweating and skin vasodilation is expected to be disclosed in the further studies. The two applied studies using QSART, Quantitative Sudomotor Axone Reflex Test, revealed that thermotolerance of tropical residents is at least in some parts acquired through long-term residence in the tropic environment after the birth and that both of the larger number of forearm sweat glands and the larger sweat output, from a single gland contribute to the men's better thermotolerance compared to the women. In combination of these approaches, studies of the mechanisms on the interrelationship of thermal sweating and active cutaneous vasodilation will be enhanced.