Presynaptic activity of the imidazolidine derivative ST 587, a highly selective alpha 1-adrenoceptor agonist.
St 587 increased the blood pressure of pithed rats. When the antagonists prazosin (alpha 1) and rauwolscine (alpha 2) were used the drug was shown to be a more selective alpha 1-adrenoceptor agonist than methoxamine. St 587 inhibited the tachycardia elicited by sympathetic stimulation in pithed rats. This effect was presynaptic and due to stimulation of alpha 1-adrenoceptors, as revealed by the different antagonism exerted by prazosin and yohimbine (alpha 2), respectively. The existence of presynaptic alpha 1-adrenoceptors is discussed.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; C030655:St 587; D007545:Isoproterenol; D003000:Clonidine