Effects of DPI (2-(3,4-dihydroxyphenylimino)-imidazolidine) on prejunctional alpha-adrenoceptors and prejunctional dopamine receptors in the rabbit ear artery.
The effects of DPI on transmitter noradrenaline release were examined in rabbit isolated ear arteries previously incubated in [ 3H ]noradrenaline. DPI (0.1 mumol/l) reduced transmitter release with periarterial electrical stimulation at 1 Hz (1 ms pulses, supramaximal voltage for 30 s), which is consistent with an agonistic effect of DPI on prejunctional alpha-adrenoceptors. At stimulation frequencies of 2 or 5 Hz DPI alone did not affect release, however in the presence of phentolamine (3 mumol/l, which increased release per se) DPI again significantly reduced release; this effect was blocked by metoclopramide (1 mumol/l) indicating an agonistic effect of DPI on prejunctional dopamine receptors.
D000818:Animals; D001158:Arteries / Q000187:drug effects; D002395:Catecholamines / Q000494:pharmacology*; D004423:Ear / Q000098:blood supply*; D004558:Electric Stimulation; D048288:Imidazolines; D008787:Metoclopramide / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism; D010646:Phentolamine / Q000494:pharmacology; D011817:Rabbits; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011954:Receptors, Dopamine / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects
D002395:Catecholamines; D048288:Imidazolines; D018377:Neurotransmitter Agents; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; C011775:(3,4-dihydroxyphenylamino)-2-imidazoline; D008787:Metoclopramide; D010646:Phentolamine