Topical thermal therapy with hot packs suppresses physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF.

Abstract

We focused on the analgesic effect of hot packs for mechanical hyperalgesia in physically inactive rats. Male Wistar rats were randomly divided into four groups: control, physical inactivity (PI), PI+sham treatment (PI+sham), and PI+hot pack treatment (PI+hot pack) groups. Physical inactivity rats wore casts on both hind limbs in full plantar flexed position for 4weeks. Hot pack treatment was performed for 20min a day, 5days a week. Although mechanical hyperalgesia and the up-regulation of NGF in the plantar skin and gastrocnemius muscle were observed in the PI and the PI+sham groups, these changes were significantly suppressed in the PI+hot pack group. The present results clearly demonstrated that hot pack treatment was effective in reducing physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF in plantar skin and gastrocnemius muscle.