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1Noll Laboratory, Department of Kinesiology and 2Graduate Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania; and 3Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland
Submitted 2 October 2006 ; accepted in final form 7 December 2006
Cutaneous vasoconstriction (VC) is the initial thermoregulatory response to cold exposure and can be elicited through either whole body or localized skin cooling. However, the mechanisms governing local cold-induced VC are not well understood. We tested the hypothesis that Rho kinase participates in local cold-induced cutaneous VC. In seven men and women (20–27 yr of age), up to four ventral forearm skin sites were instrumented with intradermal microdialysis fibers for localized drug delivery during cooling. Skin blood flow was monitored at each site with laser-Doppler flowmetry while local skin temperature was decreased and maintained at 24°C for 40 min. Cutaneous vascular conductance (CVC; laser-Doppler flowmetry/mean arterial pressure) was expressed as percent change from 34°C baseline. During the first 5 min of cooling, CVC decreased at control sites (lactated Ringer solution) to –45 ± 6% (P < 0.001), increased at adrenoceptor-antagonized sites (yohimbine + propranolol) to 15 ± 14% (P = 0.002), and remained unchanged at both Rho kinase-inhibited (fasudil) and adrenoceptor-antagonized + Rho kinase-inhibited sites (yohimbine + propranolol + fasudil) (–9 ± 1%, P = 0.4 and –6 ± 2%, P = 0.4, respectively). During the last 5 min of cooling, CVC further decreased at all sites when compared with baseline values (control, –77 ± 4%, P < 0.001; adrenoceptor antagonized, –61 ± 3%, P < 0.001; Rho kinase inhibited, –34 ± 7%, P < 0.001; and adrenoceptor antagonized + Rho kinase inhibited sites, –35 ± 3%, P < 0.001). Rho kinase-inhibited and combined treatment sites were significantly attenuated when compared with both adrenoceptor-antagonized (P < 0.01) and control sites (P < 0.0001). Rho kinase mediates both early- and late-phase cold-induced VC, supporting in vitro findings and providing a putative mechanism through which both adrenergic and nonadrenergic cold-induced VC occurs in an in vivo human thermoregulatory model.
fasudil; local cooling; vascular function; adrenergic; norepinephrine
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