Chemically and electrically induced sweating and flare reaction.

Area of Science:

• Neuroscience
• Dermatology
• Physiology

Background:

• Thin afferent (nociceptors) and efferent (sympathetic sudomotor) nerve fibers are activated by electrical and chemical stimuli, causing neurogenic erythema and sweating.
• These neurogenic responses are utilized to evaluate the functional integrity of sympathetic and nociceptor fibers in humans.

Purpose of the Study:

• To simultaneously assess electrically induced sweating and erythema on the foot dorsum and thigh.
• To compare electrically induced responses with chemically induced activation.

Main Methods:

• Simultaneous assessment of electrically induced sweating and erythema in 32 subjects.
• Comparison with chemically induced activation (acetylcholine).
• Intensity-response relations were established using stimulation intensities ranging from 0-30 mA at 1 Hz.

Main Results:

• Sweat response showed a steeper increase at lower intensities compared to erythema (18.3 mA vs. 25.7 mA, p<0.01), indicating lower electrical thresholds for sudomotor fibers.
• Electrically induced maximum flare areas (4.5 cm2) were smaller than chemically evoked ones (10.6 cm2).
• Electrically evoked sweating rate (0.31 microl/cm2/min) was higher than chemically evoked (0.21 microl/cm2/min, p<0.01).

Conclusions:

• Electrical stimulation effectively activates both sudomotor and nociceptor fibers.
• Sudomotor fibers appear to have lower electrical thresholds than nociceptors.
• Electrical stimulation may enhance sweating efficacy through synchronized sympathetic fiber discharge.