Vasodepression ex vivo after administration of inflammatory mediators in vivo in the rat

When rats were pretreated by intraplantar or i.v. injection of various inflammatory mediators, the vasopressor effect of i.a. norepinephrine in the subsequently isolated perfused hindlegs of the rats was found to be partly depressed. This vasodepression could also be detected if mediators were directly co-perfused in the isolated hindlegs. The vasodepressor effect was strongest following histamine pretreatment and co-perfusion, respectively, whereas endotoxin 0111:B4, PAF-acether, PGE1, and LTD4 were less effective. Only weak or no vasodepression could be induced by bradykinin, serotonin, lysolecithin, and substance P (1-11). The significance of the results is discussed with respect to anaphylactic disorders.