1. Prostaglandin D (DP) receptor agonists have been shown to induce hypotension in rat models, possibly via peripheral vasodilation However, it is not known which tissues and organs are most responsive. 2. In the present study, BW245C, a DP receptor-selective agonist, was administered to Inactin (Sigma, St Louis, MO, USA)-anaesthetized rats. Animals received three serial i.v. infusions (17 min each) of either BW245C (escalating doses of 0.3, 3 and 30 µg/kg; n = 6) or vehicle (6% ethanol in normal saline; n = 6). Mean arterial pressure (MAP) and heart rate were monitored continuously and regional blood flow was determined by the radionuclide-labelled microsphere method at baseline and at the end of each infusion. 3. It was found that BW245C dose-dependently reduced MAP; blood flow increased in forelimb skeletal muscle and skin, resulting in decreases in the regional vascular resistance (RVR) of skeletal muscle to -6 ± 13, -53 ± 11 and -68 ± 6% of baseline following 0.3, 3 and 30 µg/kg, BW245C, respectively (P < 0.05 vs vehicle treatment for the two higher doses), and skin to -29 ± 8, -55 ± 8 (P < 0.05) and -30 ± 16% of baseline, respectively. Relative to vehicle, blood flow and RVR for brain, heart, lung, liver, stomach and kidney were not significantly affected by BW245C. 4. These results demonstrate that the hypotension resulting from DP receptor activation in the rat is mediated primarily through vasodilation of arterioles of skeletal muscle independent of changes in blood flow to vital organs. [ABSTRACT FROM AUTHOR]