标题：Alpha-blocking Potencies of Antihypertensive Agents (Prazosin, Terazosin, Bunazosin, SGB-1534 and Ketanserin) Having with Quinazoline or Quinazolinedione as Assessed by Radioligand Binding Assay Methods in Rat Brain
摘要：The comparative effects of antihypertensive agents, quinazoline or quinazolinedione residues (prazosin, bunazosin, terazosin, SGB-1534, and ketanserin), on the binding of [3H] prazosin, [3H] p-aminoclonidine and [3H] dihydroalprenolol ([3H] DHA) to α1, α2-, and β-adrenoceptors in the rat orain were examined using radioligand binding assay methods. pA2 values were also obtained in the isolated rat aorta (α1-adrenoceptor) using phenylephrine as an agonist. A strong inhibition by these drugs of [3H] prazosin binding to α1-adrenoceptors was observed, while the inhibition of [3H] DHA binding to β-adrenoceptors and [3H] p-aminoclonidine binding to α2-adrenoceptor was found to be very weak. The rank order of antagonistic potencies of these drugs against the α1-adrenergic receptors was determined by inhibition constants (Ki) with SGB-1534=prazosin=bunazosin > terazosin > ketanserin. The pA2 value of these drugs, in contrast, had prazosin with higher pA2 value than that of SGB-1534. From these two different types of experiments, it was clear that these drugs antagonized α1-adrenoceptors even in the central nervous system, and the side chains bound to quinazoline and quinazolinedione residues may play an important role in the antagonistic potencies for α1-adrenoceptors in the central nervous system as in the peripheral tissues.
