THE PROGRESSIVE TACTILE HYPERALGESIA INDUCED BY PERIPHERAL INFLAMMATION IS NERVE GROWTH-FACTOR DEPENDENT

EXPERIMENTAL peripheral inflammation results in cutaneous mechanical h ypersensitivity, and repeated low intensity mechanical stimulation of the inflamed skin induces a progressively incrementing hyperalgesia. W e have now examined whether the elevation in nerve growth factor (NGF) induced by the inflammation contributes to this progressive hyperalge sia. An i.p. injection of anti-NGF antiserum (5 mu l g(-1)) 1h before induction of inflammation by intraplantar complete Freund's adjuvant ( CFA) injection and 24 h after, both reduced the basal inflammatory hyp ersensitivity and significantly attenuated the progressive increase of spontaneous activity, touch-, pinch- and A beta-afferent-evoked respo nses, and the progressive reduction of the mechanical threshold of bic eps femoris/semitendinosus alpha motoneurones normally evoked by repea ted (every 5 min) tactile stimulation of the inflamed hindpaw, in dece rebrate-spinal rats. NGF contributes, therefore, to the progressive ta ctile hyperalgesia elicited by repeated touch stimulation of inflamed tissue.