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Influence of vagus nerve stimulation on histamine-induced itching
A Kirchner1, H Stefan, M Schmelz
1Neurologische Klinik, Friedrich-Alexander-Universität Erlangen, Germany. annette.kirchner@neuro.imed.uni-erlangen.de
Objective:
To investigate whether vagus nerve stimulation (VNS) reduces pruritus in humans.
Background:
Recently, it has been shown that VNS has antinociceptive and antidepressant effects in humans.
Methods:
Eleven patients were investigated before (baseline) and during chronic VNS treatment. The experiments were performed at two different stimulation intensities: 2 to 5 days after implantation at a low stimulation intensity (mean intensity 0.7 +/- 0.2 mA, second session) and after 8 to 14 weeks of VNS therapy (mean intensity 1.4 +/- 0.3 mA, third session). Twelve healthy age- and sex-matched subjects were investigated using the same experimental protocol. Itch was induced by histamine-iontophoresis and quantified on a visual analogue scale (VAS). Histamine-induced flare was quantified using laser-Doppler flowmetry.
Results:
Itch was reduced by VNS from 24 +/- 8% VAS at baseline to 15 +/- 5% VAS at second session, and 19 +/- 8% VAS at third session (p < 0.05 multivariate analysis of variance). In the control group, itch remained unaltered in all three sessions (26 +/- 5% at baseline, 23 +/- 5% in the second session, and 25 +/- 5% in the third session, not significant). The flare was unaltered in both patients and control subjects.
Conclusions:
VNS may suppress pruritus in humans.