TABLE 2.

Calculated transduction coefficients of NOPR ligands

Prism 6.0 was used to calculate transduction coefficients, (τ/K_A = R), using a derivative of the Black-Leff operational model (Kenakin et al., 2012; van der Westhuizen et al., 2014). The endogenous agonist nociceptin was used as the reference ligand, and relative bias for each ligand is ΔlogR for each pathway. Arrestin ΔlogRs were subtracted from G protein ΔlogRs, and arrestin-2 from arrestin-3 ΔlogRs, then expressed as ΔΔlogR, demonstrating the level of signaling bias in terms of G protein or arrestin-3. P values were calculated by comparison with nociceptin using an unpaired two-tailed t test. Bias factor = 10^ΔΔlogR. Data are mean ± S.E.M. (n = 3–6 experiments, triplicate samples). Dashes denote antagonists for which signal cannot be calculated.

	G-protein			Arrestin3			Arrestin2			G versus Arr3			G versus Arr2			Arr3 versus Arr2
Ligand	logR	ΔlogR	P value	logR	logR	P value	logR	ΔlogR	P value	ΔΔlogR	P value	Bias Factor	ΔΔlogR	P value	Bias Factor	ΔΔlogR	P value	Bias Factor
Nociceptin	9.55 ± 0.10	0.00 ± 0.14	—	6.78 ± 0.19	0.00 ± 0.23	—	6.35 ± 0.24	0.00 ± 0.34	—	0.00 ± 0.27	—	1.00	0.00 ± 0.36		1.00	0.00 ± 0.41		1.00
MCOPPB	10.6 ± 0.1	1.01 ± 0.14a	0.007	6.24 ± 0.19	−0.54 ± 0.22	0.17	5.84 ± 0.21	−0.52 ± 0.32	0.33	1.55 ± 0.27a	0.02	35.5	1.52 ± 0.35a	0.04	33.1	0.02 ± 0.39	0.96	1.05
SCH 221,510	7.68 ± 0.08	−1.88 ± 0.13a	0.0007	5.55 ± 0.24	−1.23 ± 0.27a	0.03	5.94 ± 0.17	−0.42 ± 0.30	0.41	−0.65 ± 0.30	0.18	0.22	−1.47 ± 0.32a	0.04	0.03	−0.81 ± 0.40	0.23	0.15
NNC 63-0532	8.57 ± 0.10	−1.00 ± 0.14a	0.007	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Buprenorphine	8.35 ± 0.10	−1.22 ± 0.14a	0.004	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
RTI-819	7.20 ± 0.10	−2.36 ± 0.14a	0.0003	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
RTI-856	8.11 ± 0.10	−1.45 ± 0.14a	0.002	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—

^aValues that are statistically different from nociceptin are shown with corresponding P values.