Table 1.

Concentration–response data for ACh and NS3573 on wild-type, mutant, and concatenated α4β2 receptors expressed with different subunit ratios

SubunitsRatioImax (nA)aAChNS3573
EC50_1m)bEC50_2m)bFrac.cndF value (DFn, DFd)eEC50_1 (nm)bEC50_2m)bFrac.cndF value (DFn, DFd)e
α4:β24:138000.95830.161738 (2,197) (2,279)
α4:β220:129001.41410.142058 (2,216)4.4100.261463 (2,131)
α4:β2100:127001.91700.152480 (2,284) (2,138)
α4:β2-6-α41:124001.31300.211047 (2,116) (2,56)
α4:β2-6-α-9-β2-6-α41:133002.51300.24842 (2,80) (2,103)
  • aAverage of maximal ACh-evoked current amplitudes in X. laevis oocyte experiments. Oocytes were clamped at holding potentials ranging from −40 to −100 mV. Peak AChmax-evoked current amplitudes from each experiment were recorded and baseline subtracted. Average current levels for all experiments on a given receptor population were rounded off to two significant digits, and SEM values were typically 10%.

  • bEC50_1 and EC50_2 correspond to the high- and low sensitivity potencies observed from the wild-type α4β2 in a 4:1 ratio, respectively.

  • cFraction of the high-sensitivity component on receptors resulting in biphasic activation profiles.

  • dNumber of experiments behind the data.

  • eFor the experiments in which data were best fitted to biphasic Hill equations, the results from the best-model F test with p < 0.0001 are given as follows: F value (degrees of freedom for the numerator, degrees of freedom for the denominator).