EFFECTS OF 6-(αα-DIPHENYLACETYLPIPERAZINYL) PHENYL-5-METHYL-4, 5-DIHYDRO- 3 (2H) -PYRIDAZINONE ON RABBIT PLATELET AGGREGATION AND TXB₂, cAMP PRODUCTION

6-(αα-diphenylacetylpiperazinyl) phenyl- 5-methyl- 4,5-dihydro- 3 (2H)-pyridazinone (DMDP) is a new synthetic pyridazinone derivative. This compound was shown to inhibit AA, ADP and PAF-induced rabbit platclet aggregation, and its IC_50s were found to be 1.12±0. 1, 4. 19±0. 5 and 2. 97±0. 1 μmol/L, respectively. At the concentration range of 1～500 μmol/L, the compound was found to depress TXB₂ content and to increase cAMP levels in washed rabbit platelets in a dose--dependent manner. These might be the mechanisms of the compound on the inhibition of rabbit olatelets.