TABLE 1

Summary of ACh concentration-response data for wild-type and mutant α4β2-nAChR in HS (1:5) and LS (5:1) isoform preparations

The loop location for each mutation is shown, and the cRNA injection ratio indicates the biased receptor population (HS 1:5 and LS 5:1 α4:β2, respectively). In the LS isoform preparation (5:1 α4:β2), the ACh concentration-response data were best fit using either monophasic or biphasic fits. Specifically, mutants β2(W176A), β2(D179A), β2(D217A), and β2(Y127A) were best fit using a biphasic logistic equation (5:1 comparison of fits test results, where P < 0.05 resulted in rejection of the data being best fit using a monophasic logistic equation: α4β2 F_3,37 = 0.5804, P = 0.6316; α4β2(W176A) F_3,104 = 2.863, P = 0.0404; α4β2(T177A) F_3,38 = 0.03193, P = 0.9922; α4β2(D179A) F_3,32 = 5.328, P = 0.0043; α4β2(D217A) F_3,42 = 2.937, P = 0.0442; α4(D218A)β2 F_3,47 = 0.5280, P = 0.6652; α4β2(D116A) F_3,28 = 2.797, P = 0.0585; α4β2(Y120A) F_3,38 = 2.542, P = 0.0707l; α4β2(Y127A) F_3,33 = 4.517, P = 0.0092). I_max is the maximal ACh-induced current amplitude for each of the receptors. pEC_{50_HS} and pEC_{50_LS} is the apparent ACh potency for each receptor. The n_H values are the calculated Hill coefficients. Data are the mean ± S.E.M. Differences between groups were analyzed using one-way analysis of variance with Tukey’s post hoc comparison (see Materials and Methods).