Artificially produced meteorological changes aggravate pain in adjuvant-induced arthritic rats

To examine the effects of change in meteorological parameters on pain-related behaviors in a simulated arthritic condition, rats with an injection of complete Freund's adjuvant into the tibio-tarsal joint were exposed to low barometric pressure (20 mmHg below the natural atmospheric pressure) and low ambient temperature (7 degreesC lower than 22 degreesC) in a climate-controlled room. When the arthritic rats were exposed to these environments, the already increased number of hindpaw withdrawals in response to noxious mechanical stimulation (hyperalgesia) was further increased, and a hindpaw withdrawal response to innocuous mechanical stimulation (allodynia) began to occur. Such exposures did not influence any of the pain-related behaviors of the control rats. These results show that lowering barometric pressure and ambient temperature within the range of natural environmental fluctuation intensify pain in arthritic rats. (C) 2003 Elsevier Ireland Ltd. All rights reserved.