title: D2 dopamine receptors associated with inhibition of dopamine release from rat neostriatum are independent of cyclic AMP.
abstract: The ability of the selective D2 dopamine (DA) receptor agonist bromocriptine to inhibit potassium-induced DA release from striatal slices was measured in rats, which had been unilaterally injected with kainic acid into the left striatum, with the aim of verifying whether the central nervous system contains DA receptors whose stimulation evokes intracellular events which do not involve cyclic AMP. It was found that increasing concentrations of bromocriptine inhibited the potassium-stimulated DA release from rat striatal slices of the kainic acid-treated side with the same potency as in control slices. On the contrary, bromocriptine and the selective D1 agonist SKF 82526 completely lost the ability to inhibit or stimulate, respectively, striatal adenylate cyclase activity from the lesioned side. Our conclusion asserts that inhibition of DA release from rat striatal slices is mediated by stimulation of D2 DA receptors which are fully operative in absence of both DA-stimulated and DA-inhibited adenylate cyclase activity. These data suggest that the intracellular events that follow D2 receptor stimulation in the nigrostriatal nerve terminals may be regulated by second messengers other than cyclic AMP.
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D001971:Bromocriptine / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D004347:Drug Interactions; D018818:Fenoldopam; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors; D051381:Rats; D011954:Receptors, Dopamine / Q000502:physiology*; D017448:Receptors, Dopamine D2
chemical_list: D001552:Benzazepines; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D001971:Bromocriptine; D000242:Cyclic AMP; D018818:Fenoldopam; D011188:Potassium; D007608:Kainic Acid; D004298:Dopamine