Fig. 2.

Effect of the M1 allosteric potentiator brucine (100 μM) on N- desmethylclozapine. Dose-response curves for N-desmethylclozapine without (•) and with (○) brucine and for acetylcholine (Ach) without (▪) and with (□) brucine showed that brucine shifted the acetylcholine concentration-response curve to the left by a factor of 4.5 but shifted the N-desmethylclozapine concentration-response curve to the right by a factor of 3.5. Results shown are from a representative experiment (points represent the mean ± SEM of quadruplicate determinations) that was repeated at least three times with comparable results (mean ± SEM given in the text).