Abstract: Objective To investigate the effect of hydrogen sulfide(H₂S) on the myogenic response of cerebral arterioles in N-nitro-L-arginine methylester(L-NAME)-induced hypertensive rats.Methods Male SD rats were randomly divided into four groups: a normal control(Control) group, a NaHS(H₂S donor) group, a L-NAME group and a NaHS+L-NAME group. After 14 days, the rats were decapitated and the brains were removed, and the cerebral arterioles(150-200 μm in diameter) were isolated and cannulated for in vitro pressure perfusion. The diameters of the arterioles in response to increased perfusion pressure(from 20 to 120 mmHg, by 20 mmHg steps) were recorded.Results Rats in the Control group showed increases in cerebral arteriole diameter as the pressure was elevated from 20 to 40 mmHg, and decreases in cerebral arteriole diameter as the pressure was elevated from 40 to 100 mmHg. The myogenic response of cerebral arterioles in the NaHS group was similar to that in normal rats. Compared with the Control group, the cerebral arteriole diameter of L-NAME-induced hypertensive rats did not increase at 40 mmHg, while myogenic tone significantly increased at 40 and 60 mmHg. The addition of NaHS to the perfusate up-shift the myogenic response curve and reduced the myogenic tone of the cerebral arterioles in L-NAME-induced hypertensive rats. For the NaHS+L-NAME group, continuous injection of NaHS slowly elevated the arteriolar diameter which increased along with the rise in pressure, and reduced the effect of L-NAME on the myogenic tone of cerebral arterioles.Conclusions H₂S can reduce the myogenic response and myogenic tone of cerebral arterioles in L-NAME-induced hypertensive rats.