Interaction between the muscle metaboreflex and the arterial baroreflex in control of arterial pressure and skeletal muscle blood flow.
The muscle metaboreflex and arterial baroreflex regulate arterial pressure through distinct mechanisms. During submaximal exercise muscle metaboreflex activation (MMA) elicits a pressor response virtually solely by increasing cardiac output (CO) while baroreceptor unloading increases mean arterial pressure (MAP) primarily through peripheral vasoconstriction. The interaction between the two reflexes when activated simultaneously has not been well established. We activated the muscle metaboreflex in chronically instrumented canines during dynamic exercise (via graded reductions in hindlimb blood flow; HLBF) followed by simultaneous baroreceptor unloading (via bilateral carotid occlusion; BCO). We hypothesized that simultaneous activation of both reflexes would result in an exacerbated pressor response owing to both an increase in CO and vasoconstriction. We observed that coactivation of muscle metaboreflex and arterial baroreflex resulted in additive interaction although the mechanisms for the pressor response were different. MMA increased MAP via increases in CO, heart rate (HR), and ventricular contractility whereas baroreflex unloading during MMA caused further increases in MAP via a large decrease in nonischemic vascular conductance (NIVC; conductance of all vascular beds except the hindlimb vasculature), indicating substantial peripheral vasoconstriction. Moreover, there was significant vasoconstriction within the ischemic muscle itself during coactivation of the two reflexes but the remaining vasculature vasoconstricted to a greater extent, thereby redirecting blood flow to the ischemic muscle. We conclude that baroreceptor unloading during MMA induces preferential peripheral vasoconstriction to improve blood flow to the ischemic active skeletal muscle.
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Jasdeep
J
Kaur
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Alberto
A
Alvarez
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Hanna W
HW
Hanna
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Abhinav C
AC
Krishnan
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Danielle
D
Senador
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Tiago M
TM
Machado
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Yasir H
YH
Altamimi
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Abe T
AT
Lovelace
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Maryetta D
MD
Dombrowski
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
Marty D
MD
Spranger
Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan doleary@med.wayne.edu.
Donal S
DS
O'Leary
D000818:Animals; D062186:Arterial Pressure / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D002339:Carotid Arteries; D004285:Dogs; D005260:Female; D006339:Heart Rate; D006614:Hindlimb / Q000098:blood supply; D007511:Ischemia / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*; D009200:Myocardial Contraction / Q000502:physiology*; D011311:Pressoreceptors; D012018:Reflex; D012039:Regional Blood Flow / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*
carotid baroreceptor unloading; exercise pressor reflex; ischemic active skeletal muscle; mild dynamic exercise; sympathetic vasoconstriction