Figure 2: Sympathetic nerves, α2C-adrenoceptors and superoxide in cold-induced vasoconstriction.
From: TRPA1 is essential for the vascular response to environmental cold exposure
Blood flow was measured using FLPI in anaesthetized mice following immersion of the ipsilateral hindpaw in cold (10 °C) water and the contralateral hindpaw remained untreated. (a) % Maximum change in hindpaw blood flow from baseline to 0–2 min following cold treatment (maximum vasoconstriction) in WT mice pretreated with guanethidine (30 mg kg−1, s.c., 4 days, n=7) or control (saline, s.c., 4 days, n=7) and (b) WT mice pretreated with the α-adrenoceptor antagonist phentolamine (10 mg kg−1, i.v., n=6) or control (saline, i.v., n=6). (c) Representative trace of a cold-induced response and (d) % Change in hindpaw blood flow from baseline to 0–2 min following cold treatment (maximum vasoconstriction) in WT mice treated with the α2-adrenoceptor antagonist yohimbine (10 mg kg−1, s.c., 30 min, n=5) or control (saline, s.c., 30 min, n=5). (e) Representative trace of a cold-induced response and (f) % Change in hindpaw blood flow from baseline to 0–2 min following cold treatment (maximum vasoconstriction) in WT mice treated with the α2C-adrenoceptor antagonist JP1302 (3 μg kg−1, s.c., 60 min, n=6) or control (saline, s.c., 60 min, n=6). (g) Representative blood flow trace of a cold-induced response and (h) % Change in blood flow from baseline to 0–2 min following cold treatment (maximum vasoconstriction) in WT mice treated with the SOD mimetic TEMPOL (30 mg kg−1, i.v., 5 min, n=4) or control (saline, i.v., 5 min, n=4). Superoxide levels were measured at 2 min (maximum vasoconstriction) following cold treatment in the hindpaw tissue samples by lucigenin chemiluminescence in (i) naïve, WT mice pretreated with TRPA1 antagonist HC030031 (100 mg kg−1, i.p., 30 min) or control (10% DMSO in saline, i.p., 30 min, n=4–5) and (j) WT mice pretreated with JP1302 (3 μg kg−1, s.c., 60 min) or control (saline, s.c., 30 min, n=6–8). (k) % Change in blood flow from baseline to 0–2 min following cold treatment (maximum vasoconstriction) in WT mice treated with the mitochondria-targeted superoxide scavenger mito-TEMPO (10 mg kg−1, i.p., 60 min, n=9) or control (saline, i.p., 60 min, n=8). All error bars indicate s.e.m. *P<0.05, **P<0.01,***P<0.001 versus respective untreated, #P<0.05, ##P<0.01 versus cold-treated hindpaw (analysis of variance, Bonferroni post hoc test).
