Quantitative sudomotor axon reflex test in normal and neuropathic subjects

Abstract

We have quantified postganglionic sweat output in human subjects resulting from axon reflex stimulation using acetylcholine electrophoresis. Dehumidified nitrogen of controlled temperature and flow rate was passed through an acrylic plastic chamber placed over a defined area of skin. Sweat droplets were evaporated; humidity change was sensed by a narrow-range humidity sensor housed in a temperature-controlled compartment and was plotted on a chart recorder. The time integral (area under the curve) was continuously integrated and converted to absolute units using a derived equation. Because stimulation and recording were simultaneous, an accurate determination of the latency of the sweat response was also possible. Quantitative sudomotor axon reflex tests were performed on the left forearm and foot of 33 female and 29 male normal subjects aged 11 to 69 years. Acetylcholine, 10%, was electrophoresed for 5 mA-minutes in the forearm and 10 mA-minutes in the foot, and recording was continued for an additional 5 minutes. The mean sweat output in males was 2.7 and 3.0 times that in females in forearm and foot, respectively (p less than 0.0001). Studies in selected autonomic neuropathies confirm that quantitative sudomotor axon reflex tests will detect postganglionic sudomotor abnormalities sensitively and reproducibly.

Heat Acclimatization in Hot Summer for Ten Weeks Suppress the Sensitivity of Sweating in Response to Iontophoretically-administered Acetylcholine

“…However, the size or number of active sweat glands can change after exposure to heat (Nielsen, 1998). According to Low et al (1983), the QSART with 10% ACh and 2 mA of direct current maximally stimulate sweat gland, nevertheless, they could not confirm this finding in short-term (exposure to hot summer seasons) heat acclimatization. It is possible that 10% ACh is insufficient to activate all sweat glands after acclimatization in September.…”

“…For example, local skin heating facilitates transmitter release at the neuroglandular junction and augments glandular responsiveness to the transmitter (Ogawa & Asayama, 1986). Lee et al (1997) and Low et al (1983) demonstrated an increase in the sweating response when the skin temperature was increased. Similarly, skin vasodilatation induced by iontophoretically applied ACh causes sweat expulsion (Sugenoya et al, 1995;Morris & Shore, 1996).…”

“…Upon arrival to the climate chamber, the subjects were dressed in light clothing and rested quietly for 60 min before the experiment commenced. The QSART (Low et al, 1983;Chemali et al, 2001;Bae et al, 2006;Lee et al, 2004Lee et al, , 2008 was performed to quantitatively evaluate glandular ACh-sensitivity. The QSART capsule consists of three concentric compartments.…”

Early Detection of Orthostatic Hypotension by Quantitative Sudomotor Axon Reflex Test (QSART) in Type 2 Diabetic Patients

“…QSART is a sensitive test used to estimate the function of postganglionic peripheral sympathetic nerves, consisting of C-fibers innervating sweat glands (9). The results of QSART reflect terminal sympathetic nerve function, which maybe impaired early in diabetic peripheral neuropathy (12).…”

“…Although the Schellong test is a well-known test estimating orthostatic hypotension (OH) defined as a fall in systolic blood pressure of 30 mmHg or more when changing from lying to standing position (8), diabetic patients suffering from OHoften have severe subjective symptoms including postural weakness, faintness, visual impairment and syncope. Quantitative sudomotor axon reflex test (QSART) is a method to assess the integrity of postganglionic sympathetic sudomotorefferents whichare activated via an axon reflex by controlled iontophoretic stimulation with acetylcholine (9). It has been suggested that diabetic peripheral nerve function is disturbed in nerve length-dependent manner (10).…”