The effect of PAT pretreatment on ET-induced inflammatory hyperalgesia is compared with pretreatment with steroidal, NSAID and other analgesic tripeptides. Each bar represents the mean±s.e.mean of measurements performed on a separate group of rats (n=5) for each treatment. All measurements were performed at 9 h following the injections. The significance of differences was measured in reference to the value of saline control for each test. Abbreviations: K(D)PV, Lys. D. Pro. Val, (10 mg kg−1; 1.1 μmol); K(D)PT, Lys. D. Pro. Thr, (10 mg kg−1; 1.1 μmol); Indo; Indomethacin (4 mg kg−1; 11.2 μmol); Dex., Dexamethasone (200 μg kg−1; 1.01 μmol); PAT, peptide analogue of thymulin (114 pmol).