Related Experiment Videos
Differentiated norepinephrine spillover in human skeletal muscle
A K Karlsson1, M Elam, P Lönnroth
1Department of Neurology, Sahlgrenska University Hospital, Göteborg, Sweden.
The American Journal of Physiology
|July 1, 1997
Summary
Sympathetic nervous system activity differs between limbs. Norepinephrine (NE) spillover, a marker of sympathetic outflow, is lower in the leg than the arm, suggesting distinct limb sympathetic regulation.
Area of Science:
- Neuroscience
- Physiology
Background:
- Neurophysiological studies typically report similar sympathetic outflow to the arms and legs.
- However, microneurographic recordings suggest differentiated sympathetic outflow to the limbs, both at rest and during stress.
- This implies potential differences in norepinephrine (NE) spillover between the limbs.
Purpose of the Study:
- To investigate and compare norepinephrine (NE) spillover in the arm and leg.
- To determine if sympathetic outflow to the limbs differs and assess the role of neuronal reuptake.
Main Methods:
- Utilized a steady-state infusion of radiolabeled [3H]norepinephrine ([3H]NE) to measure NE spillover.
- Determined body composition using dual-energy X-ray absorptiometry (DXA) scans.
- Simultaneously assessed arm and leg NE spillover per 100g tissue and total limb weight.
Main Results:
- Norepinephrine (NE) spillover was significantly lower in the leg compared to the arm (0.26 vs. 1.51 pmol.min-1.100 g-1).
- This difference persisted when normalized to total limb weight (66 vs. 137 pmol/min).
- Neuronal uptake blockade with desipramine more effectively reduced NE fractional extraction in the leg (32% decrease) than in the arm.
Conclusions:
- The leg exhibits lower norepinephrine (NE) spillover than the arm.
- This finding suggests potentially lower sympathetic outflow to the leg.
- A more neuronally dependent reuptake mechanism in the leg may contribute to the observed differences in NE spillover.