Differentiation by ascorbic acid of dopamine agonist and antagonist binding sites in striatum

Ascorbic acid, which is usually included in the incubation mixture when studying dopamine (DA) receptor binding sites, inhibits the specific binding of the agonists ADTN and apomorphine but not the antagonists haloperidol and spiroperidol. Other reducing agents have a similar action. This observation is consistent with the notion that DA agonists and antagonists sites are separate and distinct. Moreover, they suggest the possibility that the number of agonist sites $\text{in vivo}$ may be modulated, in part, by the state of oxidation of the binding sites.