3H-prazosin binds specifically to ??1?-Adrenoceptors in rat brain

Abstract

Prazosin is know to block postsynaptic α-adrenoceptors. In this study ³H-prazosin has been used to label biochemically central α-adrenoceptors. In rat brain membranes ³H-prazosin bound specifically in a rapid, reversible and saturable manner to a single class of high affinity sites. The relative order of potencies for inhibition of ³H-prazosin binding was WB4101 > ARC 239 > phentolamine ≫ piperoxane > yohimbine which is a characteristic of the α₁ type of adrenoceptors. In contrast, the relative order of potencies for inhibition of ³H-clonidine binding was yohimbine > piperoxane > WB4101 > ARC239 > prazosin which is a characteristic of the peripheral ‘α₁’-and ‘α₁’-adrenoceptors. These results indicate that ³H-prazosin binds to central ‘α₁’ and ³H-clonidine to ‘α’₂-receptor and confirm the presence of two classes of α-adrenoceptors in rat brain membranes.