Table 1. Binding Kinetics and Affinity Estimates of Ligands at the D₂R WT^a.

receptor	ligand	koff (s–1)	kon (s–1 × M–1)	pKd	pKi
D2R WT	SWR-1-8	0.017 ± 0.002 (5)	3.4 ± 0.4 × 105 (3–6)	7.30 ± 0.04	8.01 ± 0.18 (3)
D2R WT	SV-III-130	0.007 ± 0.001 (11)	8.6 ± 0.5 × 105 (3–6)	8.09 ± 0.04	8.57 ± 0.05 (3)
D2R WT	SWR-1-14	0.021 ± 0.002 (4)	3.0 ± 0.4 × 105 (4–7)	7.15 ± 0.04	7.70 ± 0.13 (3)

^ak_off values were calculated from response recovery t_1/2 as k_off = ln (2)/t_1/2. See the Methods section for derivation of k_on. pK_d was calculated from the k_off and k_on estimates as K_d = k_off/k_on, while pK_i was calculated from the IC₅₀ for GIRK channel inhibition using the Cheng–Prusoff equation,²⁵ assuming a K_d of DA equaling its EC₅₀ for GIRK activation in our assay; i.e., 33 nM. The number of oocytes is shown in parentheses; for k_on, this corresponds to the number of oocytes for each data point (see Figure 1G). Data shown are means ± SEM.