抄録
Our lab reported that lowering barometric pressure (LP) by 27 hPa aggravated pain-related behaviors in chronic pain rats, and this effect was blocked by surgical lumbar sympathectomy. LP also increased systemic blood pressure (BP) and heart rate (HR) in unanesthetized neuropathic and normal rats. Therefore, we hypothesize that sympathetic nerve activity (SNA) plays an important role in pain-aggravation by LP. In the present study, I directly recorded SNA in anesthetized rats and examined its change by LP. Normal and complete Freund's adjuvant- monoarthritic rats (male SD rats) were used. Rats were anesthetized with a urethane and α-chloralose mixture, some with isoflurene. SNA was recorded from the left sympathetic nerve trunk between L3 and L5. LP in several magnitudes and speeds was done in the decompression chamber (Daikin). LP up to 45 hPa did not significantly change SNA in normal rats, although noxious pinch to the skin or lowering body temperature increased SNA. Neither BP nor HR was significantly changed by LP. Because aggravation of pain behavior was observed only in animals with persistent pain, we also exposed monoarthritic rats to LP, but without any effect. Isoflurene anesthesia did not change the results. Previous study and these results indicate that the difference from previous observation in BP and HR and absence of change in SNA might be caused by anesthesia. To examine this possibility, recording these parameters in decerebrated rats after removal of anesthesia and recording sympathetic nerve activity in conscious rats are to be done. [J Physiol Sci. 2006;56 Suppl:S236]
