Lack of interaction between alpha 2-adrenoceptors and dopamine D2-receptors in mediating their inhibitory effects on [3H]dopamine release from rat nucleus accumbens slices.
The alpha 2-adrenoceptor agonist, UK14304, dose-dependently inhibited the electrically stimulated release of dopamine (DA) from rat nucleus accumbens slices. This effect was antagonized by idazoxan, confirming that it was an alpha 2-adrenoceptor mediated effect. There was no evidence of endogenous activation of noradrenergic receptors suggesting that the alpha 2-adrenoceptor agonist was not acting presynaptically to inhibit noradrenaline release. An in vitro superfusion technique was used to investigate whether there was any interaction between alpha 2-adrenoceptors and DA D2-receptors in mediating their inhibitory effects on [3H]DA release from rat nucleus accumbens slices. alpha 2-Adrenoceptors and DA D2-receptors interact with similar second messenger systems and it was considered that they may compete for a common pool of G-proteins. The inhibitory effects of the alpha 2-adrenoceptor agonist, UK14304, and the DA receptor agonists, quinpirole, apomorphine and pergolide were not independent. However, there was no evidence of any interaction between UK14304 and the DA D2-receptor antagonists, sulpiride or haloperidol, suggesting that the two receptors do not compete for a common pool of G-proteins in mediating their inhibitory effects on DA release.
Russell
V A
VA
Department of Chemical Pathology, University of Stellenbosch, Tygerberg Hospital, R.S.A.
Lamm
M C
MC
Taljaard
J J
JJ
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001667:Binding, Competitive; D000068438:Brimonidine Tartrate; D004298:Dopamine / Q000378:metabolism*; D004558:Electric Stimulation; D004873:Ergolines / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D006220:Haloperidol / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009714:Nucleus Accumbens / Q000378:metabolism*; D010479:Pergolide / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D019257:Quinpirole; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D015398:Signal Transduction; D013469:Sulpiride / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D004873:Ergolines; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D010479:Pergolide; D000068438:Brimonidine Tartrate; D013469:Sulpiride; D019204:GTP-Binding Proteins; D006220:Haloperidol; D001058:Apomorphine; D004298:Dopamine