The effects of a long term dihydroergotoxine treatment on agonist and antagonist striatal dopamine binding sites are dose and age related

Chronic administration of dihydroergotoxine, at the two doses of 2.5 mg/kg and 5 mg/kg decreases the binding of dopamine ³H-agonists to striatal membranes. By contrast the binding of dopamine ³H-antagonists is decreased in the animals treated with the higher dose and increased in those treated with the lower one. In old rats, in which a partial loss of both ³H-antagonist and ³H-agonist binding sites is observed, the DHT treatment confirms to increase the binding of ³H-antagonists, without affecting that of ³H-agonists. Thus, aging and ergot alkaloids seem to discrimate between DA-agonist and DA-antagonist receptor sites suggesting that this receptors are separate entityes.