The inhibitory effect of opioid and alpha 2-adrenoceptor agonists on cardiac sensory neurones is pertussis toxin-insensitive.
The role of pertussis toxin-sensitive G proteins on the alpha 2-adrenoceptor and mu-opioid receptor-mediated inhibition of the efferent function of capsaicin-sensitive neurones was investigated in guinea-pig atria pretreated with guanethidine. In the presence of atropine, CGP 20712A (2-hydroxy-5-(2-[hydroxy-3-(4-[(1-methyl- 4-trifluormethyl)1H-imidazol-2-yl]-phenoxy)propyl]aminoethoxyl+ ++)-benzamide) and prazosin, [D-Ala2,NMe-Phe4,Gly5-ol]enkephalin (DAGO, 0.1-3 microM) and 2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo(4,5-d)azepine (BHT 920, 0.01-1 microM) reduced the positive inotropic effect induced by transmural stimulation of preparations obtained from control and from pertussis toxin-treated animals. These results suggest that pertussis toxin-sensitive G proteins are not involved in the inhibitory regulation of the efferent function of capsaicin-sensitive nerve terminals in cardiac tissue induced by alpha 2 and opioid receptor stimulation.
Department of Pharmacology, University of Florence, Italy.
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Amerini
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Rubino
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Mantelli
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Filippi
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Ledda
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D006168:Guinea Pigs; D006321:Heart / Q000294:innervation*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D001381:Azepines; D004745:Enkephalins; D010566:Virulence Factors, Bordetella; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C024763:talipexole; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins