Interleukin-1 beta (1 and 5 ng) produced an intense migration of neutrophils into a 6-day-old murine air-pouch at 4 h time-point. Endogenous calcitonin gene-related peptide (CGRP) was found to be involved as a mediator of interleukin-1 beta (5 ng)-induced migration, since the CGRP receptor antagonist, CGRP-(8-37), attenuated the cellular response. The polymorphonuclear leukocyte accumulation induced by both doses of interleukin-1 beta was also potentiated by exogenously added CGRP, a response blocked by CGRP-(8-37). Interleukin-1 beta also caused plasma protein extravasation into the pouch as assessed by measuring leakage of 125I-albumin. Whereas plasma protein extravasation was potentiated by CGRP, again an effect abolished by co-administration of CGRP-(8-37), the antagonist had no effect upon the plasma extravasation induced by the cytokine alone. These results suggest that endogenous CGRP is involved in mediating the cellular response but not plasma protein extravasation evoked by interleukin-1 beta and point to CGRP receptor heterogeneity.