title: alpha 2-Adrenergic agonist and antagonist activity of the respective (-)-and (+)-enantiomers of 6-ethyl-9-oxaergoline (EOE).
abstract: The (-)-enantiomer of 6-ethyl-9-oxaergoline (EOE) inhibited contractions of the field-stimulated rat vas deferens in vitro, and produced mydriasis in anesthetized rats with an order of potency 1/2 and 1/5 that of clonidine, respectively. In contrast (+)-EOE competitively antagonized these responses to both (-)-EOE and clonidine with an order of potency 1/5 that of yohimbine. The data indicate that (-)- and (+)-EOE represent an unique example of enantiomers having opposing pharmacological activities upon alpha 2-adrenoceptors.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004873:Ergolines / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D011680:Pupil / Q000187:drug effects; D051381:Rats; D013237:Stereoisomerism; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D004873:Ergolines; C034945:6-ethyl-9-oxaergoline