No effect of pertussis toxin on peripheral prejunctional alpha 2-adrenoceptor-mediated responses and on endothelium-dependent relaxations in the rat.
1. We have investigated the effects of pertussis toxin treatment on a variety of peripheral tissues in the rat. 2. Incubation with pertussis toxin (1 microgram ml-1) in vitro failed to alter the negative inotropic actions of acetylcholine in rat left atria. 3. Pretreatment with pertussis toxin (6 micrograms kg-1, i.v., 3-4 days) abolished the negative inotropic actions of acetylcholine in rat left atria. 4. Pretreatment with pertussis toxin (40 micrograms kg-1, i.v., 3-4 days) failed to alter the prejunctional inhibitory actions of the alpha 2-adrenoceptor agonist xylazine, either in terms of the isometric contraction to a single stimulus in rat vas deferens or in terms of stimulation-evoked overflow of tritium in atria pre-incubated with [3H]-noradrenaline. 5. Pretreatment with pertussis toxin (6 micrograms kg-1, i.v., 3-4 days) failed to affect, and pertussis toxin (40 micrograms kg-1, i.v., 3-4 days) potentiated endothelium-dependent relaxations of rat aorta to histamine and acetylcholine. 6. It seems unlikely that peripheral prejunctional actions of alpha 2-adrenoceptor agonists or endothelium-dependent relaxations of rat aorta involve pertussis toxin-sensitive G proteins.
Docherty
J R
JR
Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, Dublin.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects; D009469:Neuromuscular Junction / Q000378:metabolism; D037342:Pertussis Toxin; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D014649:Vas Deferens / Q000187:drug effects; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D011942:Receptors, Adrenergic, alpha; D010566:Virulence Factors, Bordetella; D006632:Histamine; D037342:Pertussis Toxin; D000109:Acetylcholine