0000000000042938
AUTHOR
Andreas Bickel
Catecholamine release in human skin--a microdialysis study.
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 liqu…
Electrically stimulated axon reflexes are diminished in diabetic small fiber neuropathies.
Axon reflex mediated flare depends on the density and the function of cutaneous C-fibers and may be impaired in diabetic neuropathy. We induced neurogenic axon reflex flare by intracutaneous electrical stimulation and analyzed size and intensity of the flare on the dorsum of the foot and ventral thigh with laser Doppler imaging (LDI). We investigated 12 diabetic subjects with small fiber neuropathies (SFNs), 5 diabetic subjects without neuropathy (NO-Ns), and 14 healthy control subjects. Five of the normal subjects were reassessed after 12 months. In comparing patients with SFN to control subjects, we found that SFN flare size but not the intensity of vasodilation (flux) was reduced on the …
Thoracoscopic sympathectomy at the T2 or T3 level facilitates bradykinin-induced protein extravasation in human forearm skin.
Background. The endogenous peptide bradykinin (BK) is an inflammatory mediator that induces nociceptor activation and sensitization as well as protein extravasation and vasodilation. Objective. To test the hypothesis if sympathectomy affects BK-induced inflammation in humans. Methods. Dermal microdialysis was employed on the volar forearm in 10 patients (21–41 years) with regional hyperhidrosis before and three months after preganglionic endoscopic transthoracic sympathetic clipping (ETSC) at the T2 or T3 level and in 10 healthy volunteers (22–36 years). After 60 minutes perfusion with Ringer's solution microdialysis fibers were perfused with BK 10−7 M and 10−5 M for 30 minutes followed …
Chemically and electrically induced sweating and flare reaction
Both thin afferent (nociceptors) and efferent (sympathetic sudomotor) nerve fibers can be activated electrically and chemically, resulting in neurogenic erythema and sweating. These reactions have been used before to assess the impairment of sympathetic and nociceptor fibers in humans. In this study, electrically induced sweating and erythema were assessed simultaneously in the foot dorsum and thigh, and were compared to chemically induced activation. Reproducible intensity-response relations (stimulation intensities 0-30 mA, 1 Hz) were obtained from 32 subjects. The steepest increase of the sweat response was induced at lower intensities as compared to that of the erythema (18.3 mA vs. 25.…
Thermal Thresholds Predict Painfulness of Diabetic Neuropathies
OBJECTIVE—Pathophysiology explaining pain in diabetic neuropathy (DN) is still unknown. RESEARCH DESIGN AND METHODS—Thirty patients with peripheral DN (17 men and 13 women; mean age 52.4 ± 2.5 years) were investigated. Fifteen patients had neuropathic pain, and 15 patients were free of pain. Patients were followed over 2 years and examined at the beginning and thereafter every 6 months. Clinical severity and painfulness of the DN were assessed by the neuropathy impairment score and visual analog scales (VASs). Cold and warm perception thresholds as well as heat pain thresholds were obtained for evaluation of Aδ- and C-fibers. Nerve conduction velocities (NCVs) and vibratory thresholds were …