TABLE 2

Intact cell apparent binding affinity constant (pK_i) values and inhibition of (-PTx) and enhancement of (+PTx) forskolin-stimulated cyclic AMP accumulation in CHO cells stably expressing either wild-type or N410Y mutant M₂ mACh receptors Data are expressed as mean (S.E.M.) values from n ≥ 3 experiments.

	pK_i	pEC₅₀^(Gi/o)	E_max^(Gi/o)	pEC₅₀^(Gs)	E_max^(Gs)	EC₅₀^(Gs)/EC₅₀^(Gi/o)
			%		%
CHO-m2 wild-type
MCh	4.97 (0.04)	6.66 (0.05)	100	5.01 (0.12)^*	100	44.7
Oxo-M	5.58 (0.02)	7.37 (0.05)	101.7 (0.7)	5.70 (0.08)^*	98.4 (4.0)	46.8
Oxo	6.02 (0.03)	7.07 (0.08)	99.1 (1.8)	5.51 (0.12)^*	36.5 (10.1)^**	36.3
Pilo	3.77 (0.04)	4.48 (0.06)	68.3 (5.4)^**	N.D.	5.2 (1.0)^**	N.D.
CHO-m2 N410Y mutant
MCh	5.92 (0.07)^***	7.63 (0.10)^***	100	6.06 (0.09)^^,^**	100	37.2
Oxo-M	6.20 (0.06)^***	7.79 (0.10)^***	104.6 (2.5)	6.53 (0.04)^^,^**	104.0 (3.8)	18.2
Oxo	6.17 (0.03)^***	7.76 (0.06)^***	103.5 (0.1)	5.82 (0.09)^*	66.8 (5.9)^^,^*	87.1
Pilo	3.70 (0.05)	5.24 (0.10)^***	83.1 (4.8)^**	N.D.	33.0 (6.0)^^,^*	N.D.

N.D., not determined.
↵* Significant differences between pEC₅₀^(Gs) and pEC₅₀^(Gi/o) values (P < 0.05; Student's t test)
↵** E_max value is significantly less than 100% (P < 0.05; one-way ANOVA, Dunnett's post-test)
↵*** Significant differences between wild type and mutant (P < 0.05; Student's t test)