Effect of 3-(2-(4-(o-methoxyphenyl)-1-piperazinyl)ethyl)-2,4(1H,3H)-quinazolinedione monohydrochloride (SGB-1534), an antihypertensive agent, on 3H-prazosin and 3H-p-aminoclonidine binding to .ALPHA.1- and .ALPHA.2-adrenoceptors in dog brain and aorta.

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Abstract
In order to assess the antihypertensive activities of SGB-1534, 3-[2-[4-(o-methoxyphenyl)-1-piperazinyl]ethyl]-2,4-(1H,2H)-quinazolinedione monohydrochloride, the effect of this drug on the 3H-prazosin, 3H-p-aminoclonidine and 3H-dihydroalprenolol (3H-DHA) bindings to .alpha.1-, .alpha.2- and .beta.-adrenoceptors in dog brain and aorta was determined by means of radioligand binding assay and compared with that of prazosin. Potent inhibition of 3H-prazosin binding to .alpha.1-adrenoceptor sites in the brain and the aorta by SGB-1534 was observed (the potency in the brain was almost the same as that of prazosin), but the inhibition of 3H-p-aminoclonidine and 3H-DHA bindings to .alpha.2- and .beta.-adrenergic binding sites by both SGB-1534 was found in a pharmacological experiment. Thus, these results suggest that the inhibitory effect of SGB-1534 at .alpha.1-adrenoceptor binding sites, but not a .alpha.2- or .beta.-adrenoceptor sites, may contribute to the hypotensive effect.