Abstract
Using rat cerebral cortex membranes, the inhibitory effect of DG-5128 against (3H)-clonidine binding was compared between low (α2L) (in the presence of EDTA) and high (α2H) affinity states (in the presence of excess magnesium) of alpha2-adrenoceptor for agonists. The Ki value (pKi=6.79) of DG-5128 in the α2L state was 6.4 times higher than the value in the α2H state. Thus, DG-5128 produces alpha2-adrenoceptor antagonism through the selective interaction with an α2L state of the receptor.
