CUTANEOUS HYPERALGESIA INDUCED BY PERIPHERAL INJECTION OF INTERLEUKIN-1-BETA IN THE RAT

The contribution of the activity of afferent fiber filaments to pain a nd hyperalgesia after administration of a plantar injection of interle ukin-1 beta (IL-1 beta) to the hind-paw skin was investigated by recor ding action potentials of the rat dorsal root in response to mechanica l and thermal stimuli. Touch stimuli were delivered by stroking with a cotton-tipped applicator and thermal stimulation was applied by cooli ng or heating of the skin. After the administration of IL-1 beta (100 pg-1 mu g), responses to touch, cold, and heat stimulation increased t o 143%, 200%, and 392%, respectively, of control values on average. IL -1 beta induced transient spontaneous discharge in 50% of experiments. The effects of IL-1 beta were apparent within 1 min. To examine respo nses to pressure stimulation, an area of 1 mm(2) of the hind-paw skin was pressed by a mechanical stimulator. IL-1 beta (0.1 pg-200 ng) decr eased the threshold value to 58% of the control pressure required for firing. IL-1 beta also increased responses to various levels of pressu re (range: 1-20 g/mm(2)). These data suggest that IL-1 beta may play a n important role in cutaneous hyperalgesia by activating polymodal rec eptors to mechanical and thermal stimulation.