Alpha 2-adrenoceptor mechanisms in guinea-pig trachea.
In the presence of propranolol tracheal strips from guinea-pigs were markedly contracted by norepinephrine and clonidine but only slightly by phenylephrine. The contractile responses to clonidine and norepinephrine were inhibited by yohimbine but not by prazosin. The specific binding of [3H]p-aminoclonidine to the microsomal fractions from guinea-pig tracheal muscle was much greater than that of [125I]BE2254. These results indicate that alpha 2-adrenoceptors are the predominant subtype of alpha-adrenoceptor in the guinea-pig trachea. The response to norepinephrine was abolished by cyclooxygenase inhibitors, suggesting the release of excitatory prostaglandins by norepinephrine. These results raise the possibility that norepinephrine interacts with alpha 2-adrenoceptors and releases prostaglandins to contract tracheal muscle.
Takayanagi
I
I
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Kawano
K
K
Koike
K
K
D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010627:Phenethylamines / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011453:Prostaglandins / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects* / Q000378:metabolism; D044024:Tetralones; D014132:Trachea / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D007457:Iodine Radioisotopes; D010627:Phenethylamines; D011453:Prostaglandins; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; D010656:Phenylephrine; C010652:BE 2254; C016986:apraclonidine; D003000:Clonidine; D009638:Norepinephrine