Leukotriene B 4 induced decrease in mechanical and thermal thresholds of C-fiber mechanonociceptors in rat hairy skin

Abstract

We have recently shown that leukotriene B 4 (LTB 4), a product of the 5-lipoxygenase pathway of arachidonic acid metabolism, sensitizes nociceptors to mechanical stimuli. The present study examined whether LTB 4 also induced a thermal sensitization of cutaneous C-fiber high-threshold mechanonociceptors (C-HTMs). C-HTMs were characterized according to their responsiveness to noxious mechanical, thermal and chemical stimuli, including glacial acetic acid, bradykinin and capsaicin. C-HTMs were found to be either heat responsive (heat C-HTMs) or heat and chemically responsive (polymodal C-HTMs). Ninety-four percent of polymodal C-HTMs and 60% of C-HTMs were sensitized to thermal and mechanical stimuli by LTB 4 (75 ng). All sensitized C-HTMs showed decreases in both thermal and mechanical thresholds. LTB 4 lowered in both subclasses of C-HTMs average thermal threshold from 45 to 35°C and produced an average decrease in the mechanical threshold of approximately 82–86%. For both heat and polymodal C-HTMs, the magnitude of LTB 4-evoked decreases in thermal and mechanical thresholds was similar to that produced by 75 ng of PGE 2. The possibility was discussed that LTB 4 may contribute to the component of hyperalgesia that is resistant to non-steroidal anti-inflammatory agents.