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 .
C0001471
adenosine receptors
C0597357
sinus node