Further examination of the inhibitory actions of alpha 1-adrenoceptor agonists in rat vas deferens.
The inhibitory actions of alpha 1-adrenoceptor agonists were examined in the isolated bisected vas deferens of the rat. The calcium entry facilitator Bay K 8644 markedly potentiated the isometric contraction to a single stimulus pulse in epididymal portions of rat vas deferens: subsequent amidephrine produced an inhibition which was antagonised by the alpha 1-adrenoceptor antagonist, prazosin, but not by the alpha 2-adrenoceptor antagonist, yohimbine. The alpha 1-adrenoceptor agonists amidephrine and cirazoline failed to inhibit the transmitter overflow to trains of pulses at a frequency of 2 Hz in epididymal portions, but also failed to abolish the nifedipine-resistant adrenergic contraction to trains of pulses at 2 Hz in epididymal portions. It is concluded that alpha 1-adrenoceptor agonists have inhibitory effects which may be by action at presynaptic alpha 1-adrenoceptors.
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Warnock
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Hyland
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Docherty
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004983:Ethanolamines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014649:Vas Deferens / Q000187:drug effects; D014991:Xylazine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D004983:Ethanolamines; D014991:Xylazine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C016980:amidephrine; D009543:Nifedipine