抄録
The exact mechanism for weather change-induced pain has not been clarified. We have demonstrated that lowering barometric pressure (27 hPa over 8 min) augments pain-related behaviors of rats rendered neuropathic by chronic constriction injury (CCI) to the sciatic nerve. In the present experiment, we introduced a new pressure chamber, which can induce lowering barometric pressure in a variety of rates, and with this chamber we tested whether lowering barometric pressure at slower decompression rates influence CCI-induced neuropathic pain in rats. To measure mechanical hyperalgesia, noxious bending force (92.2 and 197.2 mN) of von Frey hairs (VFH) were applied ten times to the plantar skin, and the number of foot withdrawals was counted. Withdrawal thresholds to the VFH stimulation were also measured. When the CCI rats were exposed to lowering barometric pressure (20 hPa lower than atmospheric pressure; LP) at the rates of 1.4, 0.67 and 0.33 hPa/min, the already increased number of foot withdrawals in response to these mechanical stimuli (hyperalgesia) was further increased, and the already decreased withdrawal threshold was further decreased. LP at the rate of 0.17 hPa/min increased the mechanical hyperalgesia to 197.2 mN VFH, and decreased the threshold. On the other hand, LP at the rates of 0.13 or 0.06 hPa/min did not influence the mechanical hyperalgesia or the threshold in CCI rats. These results show that decompression rate must be more than 0.17 hPa/min so that augmentation of neuropathic pain is caused. [Jpn J Physiol 54 Suppl:S243 (2004)]
