Swelling, edema and leakage of proteins from the vascular compartment are immediate inflammatory responses of living tissues to local injury. Xenopsin, neurotensin (NT), NT(8-13) and NAcNT(8-13) administered to male rats anesthetized with sodium pentobarbital 60 mg/kg i.p. inhibited swelling and edema in the paw induced by immersion in 58 degrees water for 1 min. The ED50 values for xenopsin. NT, NAcNT(8-13) and NT(8-13) for reducing heat-induced edema were 0.9, 1.5, 1.9 and 2.1 nmol/kg i.v., respectively. NAcNT(8-13) was chosen as a prototype for further studies because, compared to NT, it had minimal hypotensive effects. NAcNT(8-13), 4 nmol/kg i.v., injected 10 min before mechanical injury to muscle, produced by a 4 cm midline surgical incision in the rectus abdominis, or before freeze injury to the cortex, produced by applying a cold probe (-50 degrees C) to the skull for 4 min, reduced vascular leakage, measured as area of Monastral blue staining of the injured tissues. NAcNT(8-13), 4 nmol/kg i.v., also attenuated pulmonary edema induced by epinephrine bitartrate 10 micrograms/kg i.v. The ability of NAcNT(8-13) to inhibit vascular leakage was not linked to its transient hypotensive effects and it was not blocked by alpha-helical-CRF(9-41), a putative CRF receptor antagonist, or by chlorpheniramine, a H1-histamine receptor antagonist.