Botulinum toxin type A reduces capsaicin-evoked pain and neurogenic vasodilatation in human skin.
The effect of Botulinum Toxin type A (BoNT/A) on pain and neurogenic vasodilatation induced by application to the human skin of thermal stimuli and capsaicin was evaluated in a double blind study. A capsaicin cream (0.5 ml of a 0.075%) was applied to the skin of both forearms of eighteen subjects randomly pretreated with either BoNT/A (Botox) or 0.9% saline (NS). Capsaicin was applied to a skin area either inside (protocol A) or adjacent to the BoNT/A treated area (protocol B). Pre-treatment with BoNT/A did not affect thermal-specific and thermal-pain thresholds (by quantitative sensory testing). However, capsaicin-induced pain sensation (by a visual analogue scale), flare area (by acetate sheet) and changes in cutaneous blood flow (CBF, by laser Doppler flowmetry) were reduced when capsaicin was administered inside (protocol A) the BoNT/A treated area. In Protocol B, capsaicin-induced pain was unchanged, and capsaicin-induced flare/increase in CBF were reduced only in the area treated with BoNT/A, but not in the BoNT/A untreated area. Results indicate that (i) BoNT/A reduces capsaicin-induced pain and neurogenic vasodilatation without affecting the transmission of thermal and thermal-pain modalities; (ii) reduction in capsaicin-induced pain occurs only if capsaicin is administered into the BoNT/A pretreated area; (iii) reduction in neurogenic vasodilatation by BoNT/A does not contribute to its analgesic action. BoNT/A could be tested for the treatment of conditions characterised by neurogenic inflammation and inflammatory pain.
Tugnoli
Valeria
V
Department of Clinical Neuroscience, S.Anna University Hospital of Ferrara, Ferrara, Italy. vtugnoli@hotmail.com
Capone
Jay Guido
JG
Eleopra
Roberto
R
Quatrale
Rocco
R
Sensi
Mariachiara
M
Gastaldo
Ernesto
E
Tola
Maria Rosaria
MR
Geppetti
Pierangelo
P
D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D002211:Capsaicin; D004890:Erythema / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D017288:Pain Threshold / Q000187:drug effects; D012867:Skin / Q000098:blood supply / Q000294:innervation; D014664:Vasodilation / Q000187:drug effects*
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A; D002211:Capsaicin