The rate and magnitude of atmospheric pressure change that aggravate pain-related behavior of nerve injured rats.

Complaints of patients with chronic pain may increase when the weather changes. The exact mechanism for weather change-induced pain has not been clarified. We have previously demonstrated that artificially lowering barometric pressure (LP) intensifies pain-related behaviors in rats with neuropathic pain [chronic constriction injury (CCI) and spinal nerve ligation (SNL)]. In the present study, we examined the rate and magnitude of LP that aggravates neuropathic pain. We measured pain-related behaviors [number of paw lifts to von Frey hair (VFH) stimulation] in awake rats after SNL or CCI surgery, and found that rates of decompression ≥5 hPa/h and ≥10 hPa/h and magnitudes of decompression ≥5 hPa and ≥10 hPa augmented pain-related behaviors in SNL and CCI rats, respectively. These results indicate that LP within the range of natural weather patterns augments neuropathic pain in rats, and that SNL rats are more sensitive to LP than CCI rats.