Sensory denervation with capsaicin attenuates inflammation and nociception in arthritic rats

The relatively few studies that have investigated the effects of the nervous system on chronic joint disease have reported conflicting results. We have reassessed the effects of capsaicin on experimental polyarthritis with particular reference to the relationship between changes in nociception and changes in process and outcome measures of disease activity. Capsaicin pretreatment significantly attenuated both joint swelling and disease outcome as determined by quantitative radiology and histology. There was a close correlation between process measures of inflammation and mechanical hyperalgesia in both the untreated and capsaicin treated arthritic groups. The results confirm a suppression of inflammation by capsaicin and imply that the nociceptive and pro-inflammatory (neurogenic inflammation) activities of capsaicin-sensitive fibres are closely linked such that stimuli which cause pain will also induce neurogenic inflammation and vice versa.