Inhibition by dopamine agonists of dopamine accumulation following gamma-hydroxybutyrate treatment.

The increase in the dopamine (DA) concentration of rat (whole) brain induced by gamma-hydroxybutyrate was inhibited by the reputed dopamine agonists apomorphine, apocodeine, 2-bromo-alpha-ergocryptine, piribedil, ergocornine and 5,6-dihydroxy-2-dimethylaminotetralin. The last three drugs raised DA levels in saline controls. Haloperidol, which decreased DA in controls slightly, prevented any agonist-induced rise in controls. However, haloperidol antagonized only apomorphine and piribedil in regard to the inhibition of the gamma-hydroxybutyrate induced rise in DA; this neuroleptic did not affect the inhibition by the other agonists. It is concluded that these data provide evidence for local receptor control of DA synthesis and that the DA agonists do not act through a common mechanism.