Long-term effects of short-lasting early local inflammatory insult

We examined the long-term effects of a short-lasting (similar to 24 h) infl ammatory insult generated by injections of 0.25% carrageenan (1 mul/g) into the hindpaws of newborn (PO) rat pups. At P60 animals which experienced th is early inflammatory insult showed significant alterations in the withdraw al responses to noxious stimulation of the affected paws. Furthermore, in t he absence of ongoing inflammation, the withdrawal latencies to heat stimul ation and withdrawal thresholds to mechanical stimulation were increased by such experience. In the presence of ongoing CPA-induced inflammation, howe ver, the same early experience decreased these parameters of response to no xious stimulation. These data suggest that early inflammatory insult may di fferentially affect the aspects-of nociceptive circuitry involved in transi ent pain sensitivity and in inflammation-induced hyperalgesia. NeuroReport 12:399-403 (C) 2001 Lippincott Williams & Wilkins.