title: The purported dopamine agonist (3,4-dihydroxyphenylimino)-2-imidazolidine (DPI) acts as a nonselective alpha-adrenoceptor agonist in inducing hypertension, hypomotility and hypothermia in the rat.
abstract: Following peripheral administration the purported dopamine (DA) agonist (3,4-dihydroxyphenylimino)-2-imidazolidine (DPI) was shown to increase the diastolic blood pressure of pithed rats and to decrease rat motility and rectal temperature. Dose-effect relationships were established and half-maximal effective doses for the hypertensive and hypothermic response to DPI were calculated to be 4.4 nmol/kg i.v. and 2.0 mumol/kg i.p., respectively. Pretreatment with various antagonists revealed that both alpha 1- and alpha 2-adrenergic mechanisms were responsible for the DPI-induced hypertension, hypomotility and hypothermia, indicating that DPI acts as a non-selective alpha-adrenoceptor agonist. Qualitatively the DPI-induced effects were found to correlate well with those reported for its structural analogue clonidine, thus suggesting a similar mechanism of action for these agents. DA receptor antagonists appeared to lack inhibitory potency towards any of DPI-elicited responses. The results do not therefore support the designation of DPI as a DA receptor agonist.
mesh_terms: D000316:Adrenergic alpha-Agonists; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects*; D001831:Body Temperature / Q000187:drug effects*; D002395:Catecholamines / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D048288:Imidazolines; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013565:Sympatholytics / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000316:Adrenergic alpha-Agonists; D002395:Catecholamines; D048288:Imidazolines; D013565:Sympatholytics; C011775:(3,4-dihydroxyphenylamino)-2-imidazoline; D004298:Dopamine