Depletion of epinephrine in rat hypothalamus by a dopamine agonist, pergolide.
The i.p. injection of pergolide mesylate, a dopamine agonist, at doses of 0.3-0.6 mg/kg led to a decrease in epinephrine concentration in rat hypothalamus. After a 0.6 mg/kg dose of pergolide mesylate, epinephrine concentration in hypothalamus decreased within 2 hr, reached a minimum concentration at about 8 hrs, and then returned toward control values. Norepinephrine N-methyltransferase activity was not decreased after pergolide injection in vivo nor was it inhibited by pergolide added in vitro at concentrations as high as 10(-3) M. Higher i.p. doses of less potent dopamine agonists, apomorphine (10 mg/kg) and lergotrile (3 mg/kg), also decreased epinephrine concentration in hypothalamus. The pergolide-induced decrease in hypothalamic epinephrine concentration was prevented by pretreatment with haloperidol or spiperone, antagonists of dopamine receptors. Activation of dopamine receptors appears to result in a decrease in epinephrine concentration in rat brain, possibly due to enhanced release of epinephrine.
D000818:Animals; D000978:Antiparkinson Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists; D004837:Epinephrine / Q000378:metabolism*; D004873:Ergolines / Q000494:pharmacology*; D006220:Haloperidol / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010479:Pergolide; D051381:Rats; D011919:Rats, Inbred Strains; D013134:Spiperone / Q000494:pharmacology
D000978:Antiparkinson Agents; D018492:Dopamine Antagonists; D004873:Ergolines; D010479:Pergolide; D013134:Spiperone; D006220:Haloperidol; D004837:Epinephrine