Search results for "Axon reflex"
showing 10 items of 12 documents
Heat-evoked vasodilatation in human hairy skin: axon reflexes due to low-level activity of nociceptive afferents.
1996
1. Spreading vasodilatation of the axon reflex type was evoked by contact heat stimulation of the hairy skin in the human forearm (13.3 cm2 stimulus area) and was detected by laser Doppler flowmetry at 8, 19 and 30 mm distance. 2. From a base temperature of 35 degrees C, rapidly rising short heat stimuli (4 degrees C s-1, 2 s plateau) elicited vasodilatation at an average threshold of 39.4 degrees C. For slowly rising sustained heat stimuli (64 s duration) the average threshold was 39.6 degrees C (n.s.) Laser Doppler flowmetry revealed a rapid onset within about 4 s, a long duration of several minutes beyond the end of the stimulus, and a rapid spread of vasodilatation to remote skin areas.…
Spreading of sudomotor axon reflexes in human skin.
2005
Acetylcholine (ACh) activates both sudomotor fibers and primary afferent nociceptors. This leads to sudomotor and vasodilator axon reflexes, which can be diminished, for example, in neuropathies. In some neuropathies, however, there is increased axon reflex sweating, a response pattern that has never been observed for vasodilator flares.To compare both types of axon reflexes and to elucidate possible differences.In healthy young male subjects, sweat response and flare reaction in response to ACh were quantified. Constant-current iontophoresis (300 mC) of ACh was performed on the lateral lower legs. The sudomotor axon reflex was visualized with iodine starch staining, and the sweat response …
Somatotopic arrangement of sudomotor axon reflex sweating in humans
2005
Impaired sweating may be one of the first symptoms in neuropathies, and therefore the evaluation of sweating might facilitate their early detection. Sudomotor axon reflexes can be quantified by two different methods: quantitative sudomotor axon reflex testing (QSART) measures the amount of local sweating, whereas staining with the iodine starch reaction assesses the extension of the sudomotor axon reflex area. The aim of our study was to compare both tests at three different sites on the leg: foot, lower leg and thigh.QSART and iodine starch staining after iontophoretic stimulation with acetylcholine were performed on 15 male volunteers (mean age: 25; range 24-27 years) on the left resp. th…
Topical prazosin attenuates sensitivity to tactile stimuli in patients with complex regional pain syndrome
2015
Background The sympathetic nervous system may play an important role in certain forms of chronic pain. The main aim of this study was to determine whether functional blockade of α1-adrenoceptors would alter sensitivity to cutaneous stimulation in patients with complex regional pain syndrome (CRPS). Methods and Results In an initial study, high-performance liquid chromatography-mass spectrometry of intradermal interstitial fluid collected from the forearms of three healthy individuals established that the α1-adrenoceptor antagonist prazosin penetrated the skin barrier when mixed in Lipoderm® cream base. Next, we found that application of this cream to the forearm of 10 healthy participants a…
Electrically stimulated axon reflexes are diminished in diabetic small fiber neuropathies.
2004
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 …
Sudomotor testing predicts the presence of neutralizing botulinum A toxin antibodies.
2002
The increasing number of patients being treated with botulinum toxin A complex (BoNT/A) has led to a higher incidence of neutralizing anti-BoNT/A antibodies (ABAs). Because BoNT/A is known to inhibit sweating, here we report sudometry as a possibility for predicting the presence of ABA. Sixteen patients suffering from spasmodic torticollis were selected: in 2 patients, BoNT/A treatment continued to be effective, in 9 patients, the treatment effect was impaired, and in 5 patients, secondary treatment failure developed. BoNT/A (100 mouse units, Dysport; Ipsen Pharma, Berkshire, United Kingdom) was injected subcutaneously into the lateral calves. Sweating was visualized with iodine starch stai…
Facilitated neurogenic inflammation in unaffected limbs of patients with complex regional pain syndrome.
2003
Pain, edema, increased skin temperature, reddening and trophic changes characterize complex regional pain syndrome (CRPS). Recently, we have been able to show facilitated neurogenic inflammation on the affected limb. In the current study unaffected limbs were examined after resolution of the CRPS symptoms to assess possible generalized changes predisposing to CRPS. In 12 patients and in 12 healthy volunteers dermal microdialysis in combination with electrical C-fiber stimulation was employed to induce neuropeptide release. Dialysate protein concentration and axon reflex vasodilation were measured. Neither in patients nor in controls did electrical stimulation lead to protein extravasation, …
Skin innervation at different depths correlates with small fibre function but not with pain in neuropathic pain patients
2012
Background: Neuropathy can lead not only to impaired function but also to sensory sensitization. We aimed to link reduced skin nerve fibre density in different levels to layer-specific functional impairment in neuropathic pain patients and tried to identify pain-specific functional and structural markers. Methods: In 12 healthy controls and 36 patients with neuropathic pain, we assessed clinical characteristics, thermal thresholds (quantitative sensory testing) and electrically induced pain and axon reflex erythema. At the most painful sites and at intra-individual control sites, skin biopsies were taken and innervation densities in the different skin layers were assessed. Moreover, neurona…
Botulinum Toxin Type B Blocks Sudomotor Function Effectively: A 6 Month Follow Up
2003
This study analyzes the suppression of sweat gland activity by botulinum toxin type B. We injected botulinum toxin type B (between 2 and 1000 mouse units subcutaneously) in the lateral side of both lower legs in 15 healthy volunteers. Sweat tests were carried out before botulinum toxin type B injections, and at 3 wk, 3 mo, and 6 mo. We studied focal anhidrosis by iodine–starch staining and by capacitance hygrometry after carbachol iontophoresis, according to the quantitative sudomotor axon reflex test (QSART). Iodine starch staining indicated that a threshold dose of 8 mouse units botulinum toxin type B leads to anhidrotic skin spots (>4 cm2) after 3 wk. Duration of anhidrosis was prolonged…
Neurogenic Inflammation in Complex Regional Pain Syndrome (CRPS)
2008
This chapter explains symptoms and nature of neurogenic inflammation and its importance in posttraumatic complex regional pain syndrome (CRPS). Neurogenic inflammation regularly accompanies excitation of primary afferent nociceptors. It has two major components – plasma extravasation and vasodilatation. The most important mediators are the neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP). After peripheral trauma, immune reaction (e.g., cytokines) and the attempts of the tissue to regenerate (e.g., growth factors) sensitize nociceptors and thereby amplify neurogenic inflammation. This cascade of events has recently been demonstrated in rat models of CRPS employing di…