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Am J Physiol Heart Circ Physiol 296: H1868-H1877, 2009. First published April 10, 2009; doi:10.1152/ajpheart.01112.2008
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Transient receptor potential melastatin 8 channel involvement in the regulation of vascular tone

Cardiovascular Biomedical Research Centre, School of Medicine, Dentistry and Biomedical Sciences, Medical Biology Centre, Queen's University, Belfast, United Kingdom

Submitted 21 October 2008 ; accepted in final form 5 April 2009

The transient receptor potential melastatin 8 (TRPM8) channel has been characterized as a cold and menthol receptor expressed in a subpopulation of sensory neurons but was recently identified in other tissues, including the respiratory tract, urinary system, and vasculature. Thus TRPM8 may play multiple functional roles, likely to be in a tissue- and activation state-dependent manner. We examined the TRPM8 channel presence in large arteries from rats and the functional consequences of their activation. We also aimed to examine whether these channels contribute to control of conscious human skin blood flow. TRPM8 mRNA and protein were detected in rat tail, femoral and mesenteric arteries, and thoracic aorta. This was confirmed in single isolated vascular myocytes by immunocytochemistry. Isometric contraction studies on endothelium-denuded relaxed rat vessels found small contractions on application of the TRPM8-specific agonist menthol (300 µM). However, both menthol and another agonist icilin (50 µM) caused relaxation of vessels precontracted with KCl (60 mM) or the -adrenoceptor agonist phenylephrine (2 µM) and a reduction in sympathetic nerve-mediated contraction. These effects were antagonized by bromoenol lactone treatment, suggesting the involvement of Ca²⁺-independent phospholipase A₂ activation in TRPM8-mediated vasodilatation. In thoracic aorta with intact endothelium, menthol-induced inhibition of KCl-induced contraction was enhanced. This was unaltered by preincubation with either N-nitro-L-arginine methyl ester (L-NAME; 100 nM), a nitric oxide synthase inhibitor, or the ACh receptor antagonist atropine (1 µM). Application of menthol (3% solution, topical application) to skin caused increased blood flow in conscious humans, as measured by laser Doppler fluximetry. Vasodilatation was markedly reduced or abolished by prior application of L-NAME (passive application, 10 mM) or atropine (iontophoretic application, 100 nM, 30 s at 70 µA). We conclude that TRPM8 channels are present in rat artery vascular smooth muscle and on activation cause vasoconstriction or vasodilatation, dependent on previous vasomotor tone. TRPM8 channels may also contribute to human cutaneous vasculature control, likely with the involvement of additional neuronal mechanisms.

human; rat; artery

This article has been cited by other articles:

				S. Ma Letter to the editor: "Is menthol- or icilin-induced vasodilation mediated by the activation of TRPM8?" Am J Physiol Heart Circ Physiol, August 1, 2009; 297(2): H887 - H887. [Full Text] [PDF]