3H-Prazosin binds specifically to 'alpha 1'-adrenoceptors in rat brain.

Prazosin is know to block postsynaptic alpha-adrenoceptors. In this study 3H-prazosin has been used to label biochemically central alpha-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 greater than ARC 239 greater than phentolamine greater than piperoxane greater than yohimbine which is a characteristic of the alpha 1 type of adrenoceptors. In contrast, the relative order of potencies for inhibition of 3H-clonidine binding was yohimbine greater than piperoxane greater than WB4101 greater than ARC239 greater than prazosin which is a characteristic of the alpha 2 type of adrenoceptors. These results indicate that 3H-prazosin binds to central 'alpha 1'-receptors and 3H-clonidine to 'alpha 2'-receptors and confirm the presence of two classes of alpha-adrenoceptors in rat brain membranes.