Research Database PMU-SQQUID

PMU-Authors

Abstract

Dermal microdialysis might be a promising tool to investigate properties of sympathetic neurons in the skin as investigation of peripheral noradrenergic neurons in humans usually relies on highly variable vasoconstrictor reflexes or on indirect measurements like skin temperature recordings. To evaluate this technique, 21 experiments were performed in 15 healthy subjects with four intracutaneous microdialysis fibers (diameter, 200 microm; cutoff, 5 kDa) at hands or feet. After 60 min, saline perfusion tyramine at concentrations of 0.195 to 200 microg/ml was applied for 15 min followed by a 15-min saline perfusion again. Catecholamine concentrations were detected through high-performance liquid chromatography with electrochemical detection. Control experiments were performed in human skin homogenates with and without tyramine incubation. In vivo, norepinephrine (NE) concentration increased from 36.3 +/- 10.2 pg/ml to 84.4 +/- 18.4 pg/ml (P < 0.001) during stimulation with tyramine, dialysate dopamine (DA) concentration increased from 105.2 +/- 36.5 pg/ml to 7162.4 +/- 3972.4 pg/ml (P < 0.001). Both tyramine-induced NE and DA release were dose-dependent (NE: r = 0.438, P < 0.05; DA: r = 0.894, P < 0.001). In skin homogenates, tyramine incubation led to a significant increase of DA concentrations (387.0 +/- 34.8 pg/ml, controls: 13.2 +/- 2.4 pg/ml; P < 0.05), while NE and epinephrine levels remained unchanged. In conclusion, our experiments show that dermal microdialysis is capable of locally measuring catecholamines in human skin. This offers the opportunity to investigate the function of the peripheral sympathetic nervous system. Additional to non-enzymatic oxidation, DA increase probably reflects metabolic degradation of tyramine by non-neuronal pathways and therefore does not reflect local sympathetic innervation.

Useful keywords (using NLM MeSH Indexing)

Adult

Axons/drug effects

Axons/metabolism

Axons/secretion*

Catecholamines/analysis*

Catecholamines/metabolism

Catecholamines/secretion

Dopamine/analysis

Dopamine/metabolism

Dopamine/secretion

Dose-Response Relationship, Drug

Female

Humans

Male

Microdialysis/methods*

Norepinephrine/analysis

Norepinephrine/metabolism

Norepinephrine/secretion

Presynaptic Terminals/drug effects

Presynaptic Terminals/metabolism

Secretory Vesicles/drug effects

Secretory Vesicles/metabolism

Skin/innervation*

Skin/metabolism*

Sweating/drug effects

Sweating/physiology

Sympathetic Fibers, Postganglionic/drug effects

Sympathetic Fibers, Postganglionic/metabolism

Sympathetic Fibers, Postganglionic/secretion*

Tyramine/metabolism

Tyramine/pharmacology

Up-Regulation/drug effects

Up-Regulation/physiology

Vasoconstriction/drug effects

Vasoconstriction/physiology

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