Fig. 3.

Prazosin-induced vasodilation increases heat loss. A: infrared thermography (IR) of a mouse pretreatment (top) or 70 min after prazosin (bottom). Skin surface temperature measurements are on the tail (1 cm from base, T_Tail), shaved lumbar (T_Lumbar), and interscapular (T_BAT) areas and unshaved fur (T_Fur) between the T_Lumbar and T_BAT areas. B: IR images 70 min after treatment with prazosin or vehicle (water). Prazosin increased temperature of the feet (arrows) but not the ears (asterisks). C: correlation between T_Lumbar and intraperitoneal temperature (Tb) measured concurrently. Solid line is regression T_Lumbar = (0.88 ± 0.02)Tb + (3.31 ± 0.65), R² = 0.80, df = 608, n = 14 mice (mixed sex). Dotted reference line is T_Lumbar = Tb. D: T_Tail after treatment with the indicated doses of prazosin, n = 5 mice (mixed sex). E: prazosin dose response. ΔT_Tail is the change from baseline, calculated as T_Tail mean of 10 to 170 min minus T_Tail mean of −40 to −10 min, (treatment_10to170 – baseline_−40to−10). F and G: effect of prazosin on T_Tail, T_Lumbar, T_BAT, T_Fur, and Tb in control mice. The 22°C ambient temperature (Ta) is indicated, n = 9 or 10 mice/group (mixed sex). H–L: drug effect was calculated as the change from baseline (treatment_5to110 – baseline_−65to−10). Prazosin and vehicle effect were compared by unpaired t test. M–T: effect of prazosin on total energy expenditure (TEE), Tb, heat loss, and heat conductance of control and tailless mice. Drug effect was calculated as the vehicle-corrected change from baseline [(prazosin_60to180 – prazosin_{−150to−30}) – (vehicle_60to180 – vehicle_{−150to−30})]. n = 10–13 mice/group (male). Data are means ± SE, compared by unpaired t test. Prazosin dose was 2.5 mg/kg, ip, except in dose response.