4 since tolazoline and metanephrine failed to activate the presynaptic alpha-adrenoceptors of the cat nictitating membrane under experimental conditions in which they stimulated the postsynaptic alpha-adrenoceptors , these results further support the view that the presynaptic ( alpha2 ) adrenoceptors differ from the postsynaptic ( alpha1 ) adrenoceptors .
C0034784
alpha-adrenoceptors
C0001638
alpha1