Abstract: AIM: To study the effects of Hydrogen Peroxide(H₂O₂)and 11,12-epoxyeicosatrienoic acid (11,12-EET)on EDHF-mediated relaxation in the rat basilar arteries. METHODS: The relaxant effects of acetylcholine (ACh), H₂O₂, 11,12-EET, and catalase (CAT) on rat arteria basilaris in vitro were detected by vasomotoricity experiment in vitro. RESULTS: In the rat basilar arteries, preconstricted by 30 mmol/L KCl in vitro, ACh(10^-7-10^-4.5 mol/L) had the concentration-dependent relaxation effect. 3×10^-5 mol/L Nω-nitro-L-arginine-methyl-ester (L-NAME) and 10^-5 mol/L indomethacin (Indo) could partly inhibit the relaxation effect of ACh to the rat basilar arteries, but non-No/non-PGI₂-mediated relaxation was still significant (P<0.01 vs Vehicle). After using L-NAME and Indo,11,12-EET didn't produce relaxation effect in rat basilar arteries and H₂O₂ has little relaxation effect. CAT could not inhibit the relaxation effects of ACh. CONCLUSION: Our data suggest that H₂O₂ and 11,12-EET may not involve EDHF-mediated relaxation to ACh in the rat basilar arteries.

Key words: Endothelium-dependent hyperpolarizing factor, Vascular relaxation, Hydrogen peroxide, Catalase, 11,12-epoxyeicosatrienoic acid