Analgesic effects of fibroblast growth factor in the rat

Intraperitoneal (i.p.) injection of acidic fibroblast growth factor (aFGF) to Sprague-Dawley rats induced short-lasting analgesia as measured by tail-flick latency (TFL) test. The maximum effect, a 26% increase in tail-flick latency, was obtained 15 min following 1 mu g i.p. aFGF By 30 min the effect was considerably reduced, and was no longer present by 45 min after treatment. Administration of heat-inactivated aFGF or a hybrid form of aFGF (CLYT/aFGF) that, although active, is unable to cross the blood-brain barrier (BBB), caused no analgesia. Furthermore, the analgesic effects of aFGF were prevented by pretreatment with the nitric oxide synthase inhibitor, L-N-G-nitroarginine methyl ester (L-NAME). Our findings demonstrate an analgesic effect of FGF, which requires crossing of BBB and implicates the nitric oxide pathway.