The purpose of this study was to examine whether endogenous prostaglandins (PGs) modulate vascular responsiveness to adrenergic stimuli in the hindquarters of stroke-prone Spontaneously Hypertensive Rats (SHR-sp) and Wistar-Kyoto rats (WKY). Previously we have shown that synthesis of endogenous PGs in blood vessels in the rat hindquarters was greater in SHR-sp than in WKY and that high salt diet increased the level of endogenous PGs in SHR-sp but not in WKY. Vascular responses to norepinephrine (NE) and sympathetic nerve stimulation (SNS) were examined before and after indomethacin (IND), 2 mg/kg, administered intravenously. NE was administered intraarterially into the autoperfused hindquarters. Hindquarters vascular responses to these vasoconstrictor stimuli were not altered by IND in SHR-sp and WKY at the different level of endogenous PGs. These results indicate that hindquarters vasoconstriction in response to adrenergic stimuli were not altered by IND even when vascular synthesis of endogenous PGs was augmented. The results suggest that endogenous PGs do not modulate the hindquarters responses to adrenergic stimulation in rats.