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. 2011 Nov;164(5):1558–1572. doi: 10.1111/j.1476-5381.2011.01520.x

Table 2.

Competition binding affinities of different ligands obtained with [3H]RX821002 at wild-type and chimaeric α2-adrenoceptors expressed in CHO cells

Human α2A
Ligand WT (AAA) nH BBA nH CCA nH ACA nH
ARC239 1600 (1000–2600) 0.89 450 (160–1400) 0.66 820 (600–1110) 0.72 760 (480–1200) 1.02
Prazosin 1500 (800–3100) 0.84 1400 (490–2400) 1.16 820 (600–1100) 0.94 910 (600–1500) 0.89
Spiperone 1200 (870–1600) 0.94 870 (450–1800) 0.93 560 (440–730)a 1.03 500 (320–770)aa 0.86
Spiroxatrine 550 (240–1300) 1.33 69 (34–140)aa 0.92 71 (39–130)aa 1.08 91 (48–180)aa 1.51
Chlorpromazine 600 (430–870) 0.82 160 (83–310)aaa 0.89 120 (56–260)aaa 0.68 160 (100–230)aaa 1.07
Clozapine 89 (54–150) 0.91 67 (32–150) 0.69 34 (17–67) 0.58 51 (35–77) 1.13
Atipamezole 2.1 (1.5–3.1) 0.89 2.0 (0.99–4.3) 1.00 1.2 (0.95–1.5) 0.82 1.1 (0.77–1.5) 0.97
Idazoxan 22 (15–31) 0.80 15 (2.7–45) 0.97 17 (13–24) 0.91 13 (8.3–22) 0.85
Rauwolscine 1.8 (0.78–4.5) 0.53 4.4 (2.0–9.8) 0.66 0.85 (0.40–2.1) 1.02 1.6 (0.82–3.1) 0.71
Human α2B
Ligand WT (BBB) nH AAB nH CCB nH
ARC239 150 (40–570)bbb 0.74 240 (120–480) 0.72 98 (48–220) 0.74
Prazosin 47 (17–140)bb 0.79 200 (120–360) 0.82 170 (89–310) 0.89
Spiperone 12 (3.7–38)bbb 0.51 26 (11–65) 1.65 14 (6.0–38) 0.67
Spiroxatrine 2.4 (1.2–5.0)bbb/cc 0.64 6.8 (1.8–28) 2.03 1.6 (0.64–5.9) 0.91
Chlorpromazine 43 (20–100)bbb/cc 0.64 53 (20–200) 1.84 46 (18–120) 0.70
Clozapine 12 (5.0–28)bbb 0.93 18 (8.7–45) 1.09 6.7 (1.9–23) 0.64
Atipamezole 2.7 (0.56–14) 0.85 3.0 (1.7–5.6) 0.86 1.7 (0.80–4.0) 0.65
Idazoxan 24 (18–34) 1.08 37 (29–48) 0.95 30 (19–51) 0.88
Rauwolscine 1.1 (0.7–1.8) 0.97 1.2 (0.66–2.4) 1.25 2.7 (1.1–6.9) 1.02
Human α2C
Ligand WT (CCC) nH AAC nH BBC CAC nH
ARC239 130 (66–260)ddd 1.15 180 (86–380) 0.89 n.d. 77 (34–180) 0.65
Prazosin 45 (21–81)dd 0.67 110 (50–230) 0.78 n.d. 120 (55–260) 0.56
Spiperone 29 (9.2–81)ddd 0.66 26 (10–75) 0.63 n.d. 39 (18–89) 0.79
Spiroxatrine 13 (5.9–28)ddd 1.13 12 (5.8–27) 1.05 n.d. 18 (8.4–31) 0.68
Chlorpromazine 260 (150–350)dd 0.81 260 (110–720) 0.42 n.d. 230 (130–400) 0.80
Clozapine 6.5 (2.5–18)ddd 0.75 5.1 (2.6–8.2) 0.57 n.d. 1.8 (0.2–17) 0.33
Atipamezole 4.1 (2.0–9.0) 0.92 5.3 (4.8–8.3) 0.82 n.d. 10 (5.0–23) 1.16
Idazoxan 71 (20–251) 0.71 48 (21–110) 0.73 n.d. 18 (12–34) 0.89
Rauwolscine 0.47 (0.21–1.2) 0.83 0.27 (0.12–0.63) 0.78 n.d. 0.39 (0.20–0.83) 1.14

The apparent Ki (nM) and their 95% confidence intervals from three to six independent experiments, analysed using a one-site competition model. The pseudo-Hill slope (nH) was obtained using a variable slope model. Receptors are named based on the exchanged domains (see Figure 1). Statistical significances are shown with symbols (one) P < 0.05; (two) P < 0.01; (three) P < 0.001. (a) chimaera versus wild-type α2A; (b) wild-type α2A versus wild-type α2B; (c) wild-type α2B versus wild-type α2C; (d) wild-type α2A versus wild-type α2C.