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The effects of Botulinum Toxin type A on capsaicin-evoked pain, flare, and secondary hyperalgesia in an experimental human model of trigeminal sensitization.
MedLine Citation:
PMID:  16677761     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The trigeminovascular system is involved in migraine. Efficacy of Botulinum Toxin type A (BoNT-A) in migraine has been investigated in clinical studies but the mechanism of action remains unexplored. It is hypothesized that BoNT-A inhibits peripheral sensitization of nociceptive fibers and indirectly reduces central sensitization. We examined the effect of intramuscular injection of BoNT-A on an experimental human model of trigeminal sensitization induced by intradermal capsaicin injection to the forehead. BoNT-A (BOTOX) or saline was injected intramuscularly in precranial, neck and shoulder muscles to 32 healthy male volunteers in a double blind-randomized manner. Intradermally capsaicin-induced pain, flare and secondary hyperalgesia were obtained before and 1, 4 and 8 weeks after the above treatments. A significant suppressive effect of BoNT-A on pain, flare and hyperalgesia area was observed. The pain intensity area was significantly smaller in BoNT-A group (9.16+/-0.83 cm x s) compared to saline group (15.41+/-0.83cm x s) (P=0.011). The flare area was also reduced significantly in BoNT-A group (29.81+/-0.69 cm2) compared to saline group (39.71+/-0.69 cm2) (P<0.001). Similarly, the mean area of secondary hyperalgesia was significantly smaller in BoNT-A group (4.25+/-0.91 cm2) compared to saline group (7.03+/-0.91 cm2) (P=0.040). Post hoc analysis showed significant differences across the trials with a remarkable suppression effect of BoNT-A on capsaicin-induced sensory and vasomotor reactions as early as week1 (P<0.001). BoNT-A presented suppressive effects on the trigeminal/cervical nociceptive system activated by intradermal injection of capsaicin to the forehead. The effects are suggested to be caused by a local peripheral effect of BoNT-A on cutaneous nociceptors.
Authors:
Parisa Gazerani; Camilla Staahl; Asbjøn M Drewes; Lars Arendt-Nielsen
Publication Detail:
Type:  Journal Article     Date:  2006-05-04
Journal Detail:
Title:  Pain     Volume:  122     ISSN:  1872-6623     ISO Abbreviation:  Pain     Publication Date:  2006 Jun 
Date Detail:
Created Date:  2006-05-24     Completed Date:  2006-06-12     Revised Date:  2006-08-28    
Medline Journal Info:
Nlm Unique ID:  7508686     Medline TA:  Pain     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  315-25     Citation Subset:  IM    
Affiliation:
Laboratory for Experimental Pain Research, Centre for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D-3, DK-9220 Aalborg, Denmark.
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MeSH Terms
Descriptor/Qualifier:
Adult
Botulinum Toxin Type A / pharmacology*
Capsaicin / administration & dosage
Face / blood supply
Forehead
Humans
Hyperalgesia / chemically induced,  physiopathology*
Injections, Intradermal
Male
Pain / chemically induced,  physiopathology*
Pain Measurement
Pain Threshold / drug effects
Pressure
Regional Blood Flow / drug effects
Skin Temperature / drug effects
Trigeminal Nerve / drug effects*,  physiopathology*
Urticaria / chemically induced,  pathology*,  physiopathology
Chemical
Reg. No./Substance:
0/Botulinum Toxin Type A; 404-86-4/Capsaicin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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