TY - JOUR
T1 - Dynamic exercise attenuates sympathetic responsiveness of canine vascular smooth muscle
AU - Ruble, Stephen B.
AU - Valic, Zoran
AU - Buckwalter, John B.
AU - Clifford, Philip S.
PY - 2000
Y1 - 2000
N2 - The phenomenon of reduced responsiveness of the skeletal muscle arterial vasculature to sympathetic activation during exercise (sympatholysis) remains controversial. The purpose of this study was to examine the vascular effects of sympathoactivation in dynamically exercising skeletal muscle. Mongrel dogs (19-24 kg) were instrumented chronically with transit-time ultrasonic flow probes on the external iliac arteries. After pre-treatment with atropine (0.2 mg/kg), an intravenous bolus (4 μg/kg) of a nicotinic ganglion stimulant [1,1-dimethyl-4-phenylpiperazinium iodide (DMPP)] was given at rest and during treadmill exercise at graded intensities. Administration of DMPP was associated with prompt reductions in iliac blood flow and increases in arterial pressure under all conditions. There were significant reductions (P < 0.05) in iliac vascular conductance of 58 ± 4 (SE), 48 ± 3, 36 ± 5, and 16 ± 3% at rest, 3 miles/h and 0% grade, 6 miles/h and 0% grade, and 6 miles/h and 15% grade, respectively. These data demonstrate that activation of postganglionic sympathetic nerves with DMPP caused vasoconstriction in the skeletal muscle vasculature at rest and during exercise. Additionally, the magnitude of vasoconstriction was inversely related to exercise intensity. These results support the concept of exercise sympatholysis.
AB - The phenomenon of reduced responsiveness of the skeletal muscle arterial vasculature to sympathetic activation during exercise (sympatholysis) remains controversial. The purpose of this study was to examine the vascular effects of sympathoactivation in dynamically exercising skeletal muscle. Mongrel dogs (19-24 kg) were instrumented chronically with transit-time ultrasonic flow probes on the external iliac arteries. After pre-treatment with atropine (0.2 mg/kg), an intravenous bolus (4 μg/kg) of a nicotinic ganglion stimulant [1,1-dimethyl-4-phenylpiperazinium iodide (DMPP)] was given at rest and during treadmill exercise at graded intensities. Administration of DMPP was associated with prompt reductions in iliac blood flow and increases in arterial pressure under all conditions. There were significant reductions (P < 0.05) in iliac vascular conductance of 58 ± 4 (SE), 48 ± 3, 36 ± 5, and 16 ± 3% at rest, 3 miles/h and 0% grade, 6 miles/h and 0% grade, and 6 miles/h and 15% grade, respectively. These data demonstrate that activation of postganglionic sympathetic nerves with DMPP caused vasoconstriction in the skeletal muscle vasculature at rest and during exercise. Additionally, the magnitude of vasoconstriction was inversely related to exercise intensity. These results support the concept of exercise sympatholysis.
KW - Adrenergic
KW - Blood flow
KW - Sympathetic nervous system
KW - Sympatholysis
KW - Vascular conductance
UR - http://www.scopus.com/inward/record.url?scp=0033665720&partnerID=8YFLogxK
U2 - 10.1152/jappl.2000.89.6.2294
DO - 10.1152/jappl.2000.89.6.2294
M3 - Article
C2 - 11090581
AN - SCOPUS:0033665720
SN - 8750-7587
VL - 89
SP - 2294
EP - 2299
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -