title: Failure of selective antagonists (CH-38083 and idazoxan) to distinguish between prejunctional and postjunctional alpha 2-adrenoreceptors.
abstract: 1. The prejunctional alpha 2-adrenoreceptor antagonist activity of CH-38083 (7,8-(methylenedioxi)-14-alpha-hydroxyalloberbane HCl), idazoxan and prazosin was determined against B-HT 920 on the tachycardia induced by cardiac nerve stimulation in pithed rats. Antagonism of cirazoline and B-HT 920 pressor responses was used to assess postjunctional alpha 1- and alpha 2-adrenoreceptor antagonist activities. 2. CH-38083 was more potent than idazoxan in blocking pre- and postjunctional alpha 2-adrenoreceptor sites. There was no difference between the activities of the two selective alpha 2-adrenoreceptor blocking agents on pre- and postjunctional alpha 2-adrenoreceptors. 3. These data classify CH-38083 as a potent and highly selective alpha 2-adrenoreceptor antagonist in vivo and further support evidence of the homogeneity of pre- and postjunctional alpha 2-adrenoreceptors.
authors.affiliation: Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
authors.forename: G
authors.initials: G
authors.lastname: Lonart
authors.forename: L G
authors.initials: LG
authors.lastname: Harsing
authors.forename: G
authors.initials: G
authors.lastname: Folly
authors.forename: E S
authors.initials: ES
authors.lastname: Vizi
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001599:Berberine / Q000031:analogs & derivatives / Q000494:pharmacology*; D001600:Berberine Alkaloids / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D003655:Decerebrate State; D004146:Dioxanes / Q000494:pharmacology*; D004147:Dioxins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D019329:Idazoxan; D008297:Male; D009469:Neuromuscular Junction / Q000187:drug effects; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
chemical_list: D000317:Adrenergic alpha-Antagonists; D001381:Azepines; D001600:Berberine Alkaloids; D004146:Dioxanes; D004147:Dioxins; D011942:Receptors, Adrenergic, alpha; D001599:Berberine; C048886:7,8-(methylenedioxy)-14-hydroxyberbane; C024763:talipexole; D011224:Prazosin; D019329:Idazoxan