TABLE 1

Effects of Erythrina alkaloids on [3H]cytisine binding to α4b2 nAChR and [3H]epibatidine binding to α7 nAChR

Data represent the mean ± S.E.M. of three to four experiments. For both [3H]cytisine and [3H]epibatidine bindings, the radiolabeled ligand concentration was 1 nM. Ki values were calculated by using the Cheng and Prusoff (2003) equation, Ki = IC50/1 + x/KD. The KD value for [3H]cytisine binding was 0.4 nM (Houlihan et al., 2001) and for [3H]epibatidine binding it was 1 nM.

CompoundKi
[3H]Cytisine Binding to α4β2 nAChR[3H]Epibatidine Binding to α7 nAChR
nM
DHβE98 ± 610,500 ± 400
Erysodine50 ± 3**7500 ± 150**
O-Acetylerysodine79 ± 87340 ± 230**
Erysopine154 ± 6**14,670 ± 1000*
Erysotrine604 ± 5***N.E.
Epierythratidine710 ± 9***N.E.

  • N.E., no effects at the highest concentration of inhibitor tested, 1 mM.

  • ↵* , P < 0.05;

  • ↵** , P < 0.01;

  • ↵*** , P < 0.001, relative to the effects of DHβE.