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汗。为了阐明其关系和神经机制，我们研究了前臂皮肤注射尼古丁和乙酰胆碱后的出汗和皮肤血流反应。轴突反射介导的出汗和皮肤血流量的平行关系表明，轴突反射出汗也伴随着皮肤血管扩张。阿托品消除出汗而不是皮肤血管扩张，表明血管扩张不是由M受体介导的。在猫爪出汗模型中，血管扩张与人类一样伴随着出汗。众所周知，乙酰胆碱是人类出汗的主要媒介，通过内皮产生一氧化氮(NO)来诱导血管扩张。人们强烈期望NO参与热汗的形成。由于已知的血管扩张多肽如VIP、CGRP和ANP存在于汗腺周围，NO可能通过这些多肽作用于皮肤血管和汗腺。NO介导的出汗和皮肤血管扩张机制的联系有望在进一步的研究中被揭示。QSART(定量运动轴突反射试验)的两项应用研究表明，热带居民的耐热性至少有一部分是在出生后长期居住在热带环境中获得的，前臂汗腺数量较多和单个腺体产生的汗量较大都有助于男性比女性具有更好的耐热性。将这些方法结合起来，将加强对热汗和主动皮肤血管扩张相互关系的研究。

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.