Pharmacological properties of the enantiomers of idazoxan: possible separation between their alpha-adrenoceptor blocking effects.

The alpha-adrenoceptor blocking properties of the two enantiomers of idazoxan have been investigated in rats, dogs and chicks, as well as their agonistic effects in pithed rats. At peripheral sites, (+) idazoxan was equipotent for blocking both postsynaptic alpha-1 and alpha-2 adrenoceptors of the rat and revealed to be a potent antagonist at presynaptic sites of rats and dogs. (-) Idazoxan revealed to be selective for postsynaptic alpha-2 adrenoceptors with an apparent selectivity ratio of about 10.

Specific binding of 3H-guanfacine to alpha 2-adrenoceptors in rat brain. Comparison with 3H-clonidine.

1. 3H-clonidine and the new antihypertensive drug, 3H-guanfacine (N-amino-2-[2,6-dichlorophenyl]-acetamide hydrochloride), bind with a high affinity to alpha 2-adrenoceptors in the rat central nervous system. 2.

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.