No effect of pertussis toxin on peripheral prejunctional α2‐adrenoceptor‐mediated responses and on endothelium‐dependent relaxations in the rat

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Abstract
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 μg ml−1) in vitro failed to alter the negative inotropic actions of acetylcholine in rat left atria. 3 Pretreatment with pertussis toxin (6 μg kg−1, i.v., 3–4 days) abolished the negative inotropic actions of acetylcholine in rat left atria. 4 Pretreatment with pertussis toxin (40 μg kg−l, i.v., 3–4 days) failed to alter the prejunctional inhibitory actions of the α2-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 μg kg−1, i.v., 3–4 days) failed to affect, and pertussis toxin (40 μg 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 α2-adrenoceptor agonists or endothelium-dependent relaxations of rat aorta involve pertussis toxin-sensitive G proteins.

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