[Cardiovascular effect of a novel substance, 3-[2-[4-(o-methoxyphenyl)-1-piperazinyl] ethyl]-2,4 (1H, 3H)-quinazolinedione monohydrochloride (SGB 1534)].

During the search for a new antihypertensive substance, the author and his co-workers found that SGB 1534 has a potent vasodepressor action. However, its pharmacological properties are not well-known. Therefore, we examined the cardiovascular effect and the site of action of this substance. In anesthetized beagle dogs, SGB 1534 (0.01 micrograms/kg, i.v.) caused a 8% fall in mean systemic blood pressure. It caused a transient increase in aortic blood flow. Heart rate was increased transiently and was decreased thereafter. Systemic vascular resistance was reduced, but Vpm and time constant "T" were little influenced by this substance. The phenylephrine-induced vasopressor effect was eliminated by SGB 1534. In dogs pretreated with propranolol and prazosin, the norepinephrine-induced vasopressor effect was suppressed by yohimbine, but not by SGB 1534. In dogs pretreated with prazosin and yohimbine, isoproterenol-induced increase in heart rate was not influenced by this substance. The results indicate that SGB 1534 is a potent alpha 1-adrenoreceptor blocking substance.