ISSN:
1432-1912
Schlagwort(e):
Adenosine
;
Carbachol
;
K+ channels
;
Pertussis toxin
;
Atrioventricular block
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Summary The influence of pertussis toxin on the effects of adenosine, the adenosine receptor agonist (−)-N6-phenylisopropyladenosine (PIA) and the m-cholinoceptor agonist carbachol on heart rate and atrioventricular (AV) conduction was investigated in spontaneously beating isolated perfused guinea-pig hearts. In addition, the effects of the agents on the electrocardiogram recorded from anesthetized guinea pigs were studied. Adenosine (0.1–100 μmol/l) and PIA (0.001–100 μmol/l) had concentration-dependent negative chronotropic and negative dromotropic effects. These effects were prevented by pretreatment of the animals with pertussis toxin (150 μg/kg; i.v.). Carbachol (0.001–100 μmol/l) had similar cardiac depressant effects. These effects were also abolished by pertussis toxin. In contrast, the negative chronotropic and negative dromotropic effects of the calcium antagonist verapamil which was investigated for comparison were not influenced by pretreatment with pertussis toxin. Since the cardiac depressant effects mediated via adenosine receptors or via m-cholinoceptors are most probably due to an activation of a K+ conductance, it is concluded that both receptors in the sinus node and in the AV node may be coupled via a common pertussis toxin-sensitive guanine nucleotide-binding protein to the K+ channel. It remains to be elucidated whether an additional inhibitory coupling to Ca2+ channels also plays a role.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00165137
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