Repeated intradermal injection of low-dose carrageenan induces tachyphylaxis to evoked hyperalgesia.
Changes in the thresholds to noxious mechanical and thermal stimulation were monitored in a group of normal sheep at different times (30 min-24 h) following intradermal injection of either low-dose (0.0625%) carrageenan, a widely used mucopolysaccharide irritant, or saline (0.9%) into the lateral aspect of the fore limb. Thresholds to noxious mechanical stimulation were measured on the ipsilateral limb whereas thresholds to noxious thermal stimulation were measured at a site distant to that of the injection, the ipsilateral ear. During the first 2 h after carrageenan injection the thresholds to noxious thermal stimulation fell, while thresholds to noxious mechanical stimulation were unaltered. The evoked hyperalgesia was reversed by the administration of non-steroidal anti-inflammatory agents. Hyperalgesia was not present 4 h after carrageenan injection in control or treated animals. This experiment was carried out on 3 further occasions and a diminishing response to injection of carrageenan was observed, suggesting development of tachyphylaxis to evoked thermal hyperalgesia.
Welsh
Elizabeth M
EM
Department of Veterinary Pharmacology, University of Glasgow Veterinary School, Bearsden, Glasgow G61 1QH, Scotland UK.
Nolan
Andrea M
AM
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D002351:Carrageenan / Q000008:administration & dosage; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology*; D007271:Injections, Intradermal; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation; D012756:Sheep; D012867:Skin / Q000033:anatomy & histology; D012881:Skin Temperature / Q000502:physiology; D013618:Tachyphylaxis / Q000502:physiology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D002351:Carrageenan