title: The purported dopamine agonist DPI inhibits [3H]noradrenaline release from rat cortical slices but not [3H]dopamine and [14C]acetylcholine release from rat striatal slices in-vitro.
abstract: The effects of the purported dopamine (DA) receptor agonist (3,4-dihydroxyphenylimino)-2-imidazolidine (DPI) upon the in-vitro K+-induced release of [3H]DA and [14C]acetylcholine from rat neostriatal slices, and of [3H]noradrenaline from rat neocortical slices have been investigated and compared with those of the DA receptor agonist TL-99 and the alpha-adrenoceptor agonist clonidine, respectively. The rapid decomposition of the catechol compounds DPI and TL-99 in the Krebs-Ringer bicarbonate superfusion medium was shown to be inhibited by both the chelating agent EDTA and the reducing agent ascorbic acid. The results suggest that in-vitro DPI is unable to stimulate striatal DA receptors, whereas it is effective in stimulating cortical alpha 2-adrenoceptors (EC50 = 61 nM). It is concluded that DPI should be considered as a mixed alpha 1/alpha 2-adrenoceptor agonist and that the designation of DPI as a DA receptor agonist should be abandoned.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D048288:Imidazolines; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D002395:Catecholamines; D048288:Imidazolines; D013764:Tetrahydronaphthalenes; D015016:Yohimbine; C016893:2-(N,N-dimethylamino)-6,7-dihydroxytetralin; C011775:(3,4-dihydroxyphenylamino)-2-imidazoline; D000109:Acetylcholine; D011188:Potassium; D004298:Dopamine; D009638:Norepinephrine