Alpha 1-adrenoceptor subtypes mediating the norepinephrine-induced contractile response in the rat vas deferens.
1. The effects of chlorethylclonidine (CEC), 5-methyl-urapidil (5-MU), ryanodine and prolonged exposition to norepinephrine (NE) on the concentration-response curves (CRC) to this agonist on the bisected rat vas deferens (RVD) were investigated. 2. CEC did not affect the 50% effective concentration (EC50) of NE in either the prostatic (PP) or the epididymal (EP) portions of the RVD. 3. 5-MU did not alter the EC50 of NE in the PP but caused a significant and concentration-dependent rightward shift of the CRC to NE in the EP. 4. Ryanodine caused a shift to the right of the CRC to NE in the PP associated to a decrease in maximal response, but did not affect the CRC to NE in the EP. 5. Incubation of the EP with NE for 6 hr elicited a significant decrease in the maximal response with no changes in the EC50. Similar treatment of the PP was associated with a significant shift to the right of the CRC to NE without modifications in the maximal response. 6. These results suggest that in the RVD, NE interacts with two different alpha 1-adrenoceptors subtypes which are disposed in a selective manner along the RVD: the alpha 1(a) subtype in the EP, and non-alpha 1b-non-alpha 1a adrenoceptor subtype mainly located at the PP.
Queiroz-Neto
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A
Department of Animal Morphology and Physiology, Faculty of Agronomic and Veterinary Sciences, University of São Paulo State-UNESP, Jaboticabal, Brazil.
Ballejo
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D058668:Adrenergic alpha-1 Receptor Antagonists; D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004822:Epididymis / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D011467:Prostate / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects
D058668:Adrenergic alpha-1 Receptor Antagonists; D000477:Alkylating Agents; D010879:Piperazines; D018340:Receptors, Adrenergic, alpha-1; D012433:Ryanodine; C057446:5-methylurapidil; C051731:chlorethylclonidine; D003000:Clonidine; D009638:Norepinephrine