Activation of the cortical pain network by soft tactile stimulation after injection of sumatriptan.
The anti-migraine drug sumatriptan often induces unpleasant somatosensory side effects, including a dislike of being touched. With a double-blind cross-over design, we studied the effects of sumatriptan and saline on perception (visual analogue scale) and cortical processing (functional magnetic resonance imaging) of tactile stimulation in healthy subjects. Soft brush stroking on the calf (n=6) was less pleasant (p<0.04) and evoked less activation of posterior insular cortex in the sumatriptan compared to the saline condition. Soft brushing activated pain processing regions (anterior insular, lateral orbitofrontal, and anterior cingulate cortices, and medial thalamus) only in the sumatriptan condition, whereas activation of somatosensory cortices was similar in both conditions. Soft brush stroking on the palm (n=6) was equally pleasant in both conditions. One possible mechanism for the activation of pain processing regions by brush stroking is sensitization of nociceptors by sumatriptan. Another possibility is inhibition of a recently discovered system of low-threshold unmyelinated tactile (CT) afferents that are present in hairy skin only, project to posterior insular cortex, and serve affective aspects of tactile sensation. An inhibition of impulse transmission in the CT system by sumatriptan could disinhibit nociceptive signalling and make light touch less pleasant. This latter alternative is consistent with the observed reduction in posterior insular cortex activation and the selective effects of stimulation on hairy compared to glabrous skin, which are not explained by the nociceptor sensitization account.
Krämer
Heidrun H
HH
Department of Neurology, Johannes Gutenberg University, Mainz, Germany. hekr@neuro.gu.se
Lundblad
Linda
L
Birklein
Frank
F
Linde
Mattias
M
Karlsson
Tomas
T
Elam
Mikael
M
Olausson
Håkan
H
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply / Q000187:drug effects / Q000503:physiopathology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood; D010146:Pain / Q000188:drug therapy* / Q000209:etiology; D010147:Pain Measurement; D017288:Pain Threshold; D010812:Physical Stimulation / Q000009:adverse effects; D017366:Serotonin Receptor Agonists / Q000627:therapeutic use*; D012867:Skin / Q000294:innervation; D018170:Sumatriptan / Q000627:therapeutic use*; D014110:Touch / Q000502:physiology*
D017366:Serotonin Receptor Agonists; D018170:Sumatriptan; D010100:Oxygen