Study on the role of nitric oxide on sweating

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Reflex control of skin blood flow in human is accomplished through sympathetic vasoconstrictor nerves and a sympathetic active vasodilator system. Cutaneous active vasodilation is closely related to the activation of sweat glands and is suggested to be mediated by peptidergic cotransmitters, such as VIP or CGRP, of the cholinergic sympathetic nerve. However, the mechanisms of active vasodilator system is not fully understood, because of the lack of the animal model. Therefore, we tried to develop a cat paw model. In 4 anesthetized cats, sweating on the paw pad was measured by a ventilated capsule method and skin blood flow was measured with a laser-Doppler flowmeter. Spontaneous sweating was disappeared after anesthesia. Local and systemic administration of accetylcholine (ACh) and pilocarpine induced sweating without cutaneous vasodilation. Electric stimulation of the tibial nerve induced sweating with cutaneous vasodilation on the hind paw. Video-microscope (× 25-175) enabled us to o … More bserve sweat emergence from the gland pores, and showed the sweat gland density of about 13-15 per mm^2. These results indicate that cat paw is a useful animal model to study the mechanisms of cutaneous active vasodilation. In the human subjects, on the ventral surface of the forearm nicotine (10^<-4> g/ml, ip) was administered, and sweat rate and cutaneous blood flow were measured at the sites beyond a rubber band bound around the arm. Nicotine induced axone-reflex sweating as well as skin vasodilatation, and the both responses parallely changed throughout observation period. The previously administered atropine blocked the sweating response induced by nicotine, but failed to block the cutaneous vasodilatation on the same area. The results indicate that skin vasodilatation accompanied with axone-reflex sweating is probably mediated, not by muscarinic action of a ACh, but by some vasodilative polypeptides, such as VIP or CGRP co-released with ACh from the postganglionic sudomotor nerve terminals. Further understanding is expected through the pharmaceutical approaches using selective blockers of these vasoactive peptide in the useful cat paw sweating model. Less