The effects of CU-763-10-01 on rat and rabbitblood pressure and on isolated smooth musclecontraction were investigated. The contractionactivated by different agents in physiological solutionwere compared in rat aorta, rat vas deferens, rabbitaorta and guinea-pig trachea. Pre-incubation withCU-763-10-01 5x10('-5) M showed significant inhibition onrat aorta and rat vas deferens contraction induced byKCl, BaCl(,2), 5-HT and NE. In rabbit aortaCU-763-10-01 can inhibit significantly contractioninduced by both KCl and BaCl(,2) but not 5-HT or NE.CU-763-10-01 also inhibit guinea-pig tracheacontraction activated by histamine. In calcium-freesolution, CU-763-10-01 produced a significantinhibition of the KCl and NE-induced contraction. Inpotassium depolarizing solution, CU-763-10-01 produceda concentration-ralated rigthward shift of a cumulativecalcium concentration response curve. The NE-inducedcontraction on rat aorta was non-competitivelyantagonized by CU-763-10-01 with low affinity. Basedupon blocked of blood pressure in rat and rabbit,CU-763-10-01 produced significant transient loweringblood pressure. These results suggest that themechanism of action of CU-763-10-01 may involve theinterferring of calcium influx and calcium release fromcalcium-store.