Effect of PAF on selected smooth muscle preparations.

The myotropic activity of PAF (Platelet activating factor) was studied on selected smooth muscle preparations from the rat and the guinea-pig, and compared with the responses to histamine, acetylcholine, norepinephrine, leukotriene D4 (LTD4), prostaglandin (PG) E2 and F2 alpha. Our results showed that nanogram quantities of PAF induced strong contractile responses. Tachyphylaxis appeared as a common feature of PAF activity. The responses were usually slow in onset and sustained. Leukotriene D4 and prostaglandin E2 also contracted most tissues used except the lung tissues where prostaglandin E2 induced a relaxation.