L. Hejnova et al., POSITIVE AND NEGATIVE ALLOSTERIC INTERACTIONS ON MUSCARINIC RECEPTORS, European journal of pharmacology. Molecular pharmacology section, 291(3), 1995, pp. 427-430
It was previously found that alcuronium increases the binding of [H-3]
methyl-N-scopolamine to cardiac muscarinic receptors by a positive all
osteric action while its effect on the binding of [H-3]quinuclildinyl
benzilate is negative. The features of the antagonist's molecule which
decide whether its allosteric interaction with alcuronium is positive
or negative are not known. In the present work, it was found that alc
uronium has a positive allosteric effect also on the binding of [H-3]a
tropine and [H-3]methyl-N-piperidinyl benzilate to muscarinic receptor
s in rat heart atria and that its effect on the binding of [H-3]methyl
-N-quinuclidinyl benzilate is negative. A comparison of the five radio
labelled antagonists that have been investigated so far indicates that
the type of allosteric interaction (positive or negative) is not dete
rmined by the presence or absence of the quaternary nitrogen or of the
benzilyl moiety in the molecule of the antagonist. Apparently, featur
es of the N-bearing moiety of muscarinic antagonists other than the pr
esence of a charge an nitrogen play a key role in the determination of
the type of interaction.