A novel 5-HT(2) antagonist, sarpogrelate hydrochloride, shows inhibitory effects on both contraction and relaxation mediated by 5-HT receptor subtypes in porcine coronary arteries.

In isolated porcine coronary arteries, concentrations of 5-HT (10(-8) to 3x10(-5) mol/l), alpha-methylserotonin (alpha-Me-5-HT, 10(-8) to 3x10(-5) mol/l) and ergonovine (10(-9) to 3x10(-4) mol/l) produced contraction, whereas high concentrations (10(-5) to 10(-4) mol/l) of these drugs produced relaxation. Both sarpogrelate and ketanserin produced rightward shifts of contraction concentration-response curves induced by 5-HT and alpha-Me-5-HT at the concentration from 10(-9) to 3x10(-5) mol/l, and only sarpogrelate inhibited the relaxation at high concentrations of 5-HT and displayed 155% of maximal contraction at 10(-4) mol/l 5-HT. On the other hand, sarpogrelate and ketanserin did not show any inhibitory effects on the relaxation induced by high concentrations of ergonovine. These results suggested that sarpogrelate and ketanserin show different inhibitory effects on the relaxation induced by high concentrations of 5-HT, indicating that these two drugs may have different affinities to 5-HT receptor subtypes that may be involved in relaxation.