Antinociceptive effect of botulinum toxin type a in rat model of carrageenan and capsaicin induced pain.
OBJECTIVE
To test antinociceptive properties of botulinum toxin type A (BTX-A) in rats with carrageenan- and capsaicin-induced pain and inflammation.


METHODS
Pain was provoked with carrageenan (1%) or capsaicin (0.1%) injection into the plantar surface of the rat paw-pad. The effect of BTX-A 5 U/kg on carrageenan- and capsaicin-induced mechanical and thermal hypersensitivity, as well as the size of carrageenan-induced paw edema were tested 24 hours and 6 days following the toxin injection into the rat paw-pad. In the dose-response experiment, the effect of different doses of BTX-A (2, 3, 3.5, 5, and 7 U/kg) on carrageenan-induced mechanical hypersensitivity was investigated on day 5 after BTX-A application.


RESULTS
Pretreatment with 5 U/kg BTX-A significantly reduced or completely abolished the enhanced sensitivity to mechanical and thermal stimuli provoked by peripheral carrageenan or capsaicin injections. This reduction was significant when BTX-A was applied 6 days before the induction of pain and inflammation, but the toxin was ineffective when applied 24 hours before the challenge. In the dose-response experiment, the lowest effective dose was 3.5 U/kg, but apparently the effect was not dose-dependent. In contrast to the antinociceptive effect, 5 U/kg BTX-A had no effect on the carrageenan-induced paw edema.


CONCLUSIONS
The study demonstrated the efficacy of peripherally applied BTX-A pretreatment on the pain component of inflammatory process in experimental animals.
Bach-Rojecky
Lidija
L
Department of Pharmacology and Croatian Institute of Brain Research, Zagreb University School of Medicine, Salata 11, 10000 Zagreb, Croatia.
Lacković
Zdravko
Z
D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology / Q000627:therapeutic use*; D002211:Capsaicin; D002351:Carrageenan; D006614:Hindlimb / Q000187:drug effects / Q000503:physiopathology; D006930:Hyperalgesia / Q000139:chemically induced / Q000188:drug therapy; D008297:Male; D023421:Models, Animal; D009619:Nociceptors / Q000187:drug effects; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy*; D051381:Rats; D017208:Rats, Wistar
D002351:Carrageenan; D019274:Botulinum Toxins, Type A; D002211:Capsaicin