AIM Our investigation is to screen bioactive novel compounds using the isolated rat aortic rings and depending on the similar and distinct characteristics between the endothelial target for acetylcholine(ETA) and muscarinic receptors and to investigate the mechanisms of vasodilatory effects of candidate compounds. METHODSIn isolated rat aorta precontracted with NE, the vasodilatory effects of novel structure compounds were investigated. We Compared the maximal relaxation of endothelium denuded aorta with that of the endothelium intact aorta elicited by the 8 candidate compounds respectively. The aortas were precubated with L NAME, indomethacine and atropine before using NE, and measured the changes of the maximum vasodilatory rate of candidate compound. RESULTS AND CONCLUSION Among 81 compounds, we found 8 novel compounds which induced relaxation. Their maximal relaxation rates ranged of from 50 percent to 85 percent. The endothelium dependent relaxation induced by DMHPPP and PPVP was blocked by indomethacin and L NAME, but not by atropine. DMHPPP and PPVP also enhanced the maximal endothelium dependent relaxation induced by acetylcholine. These suggest that novel compounds may regulate functions of endothelial cell target for acetylcholine(ETA) to induce relaxation of isolated rat aortic rings, which may involve the prostacycline and nitric oxide pathways.