Table 1. Opioid-induced antinociception assays used in MOR drug discovery.

Compound	Antinociception assay – species	Strain	Temp & cut-off	Reference
TRV130	Hot plate – mouse	C57/BL6J	56 °C, 30 s	(DeWireet al., 2013)
		C57/BL6	54 °C, 20 s	(Gillis, Gondin, et al., 2020)
		ICR	55 °C, 30 s	(Mori et al., 2021)
	Tail flick – mouse	Swiss Webster	52 °C,10 s	(Altarifi et al., 2017)
		C57/BL6	Variable, 10 s	(Liang, Li, Nwaneshiudu, Irvine, & Clark, 2019)
	Hot plate – rat	Sprague-Dawley	52 °C, 30 s	(DeWireet al., 2013)
	Tail flick – rat	Sprague-Dawley	Variable, 15 s	(DeWireet al., 2013)
		Sprague-Dawley	50 °C, 20 s	(Schwienteck et al., 2019)
TRV0109101	Hot plate – mouse	C57/BL6	56 °C, 30 s	(Koblish et al., 2017)
	Hot plate – rat	Sprague-Dawley	52 °C, 30 s
	Tail flick – rat	Sprague-Dawley	Variable, 15 s
	Von Frey filaments – mouse	C57/BL6	0.4g
PZM21	Hot plate – mouse	C57/BL6J	55 °C, 30 s	(Mangliket al., 2016)
		C57/BL6J	52.5 °C, 30 s	(iKudla et al., 2019)
		C57/BL6	54 °C, 20 s	(Gillis, Gondin, et al., 2020)
		CD-1	52.5 °C, 30 s	(Hill et al., 2018)
	Tail flick – mouse	C57/BL6J	56 °C,10 s	(Mangliket al., 2016)
		C57/BL6J	Variable, 9 s	(iKudla et al., 2019)
	Affective vs reflexive – hot plate – mouse	C57/BL6J	52.5 °C, 30 s	(Mangliket al., 2016)
	Formalin chemical assay – mouse	C57/BL6J	1% formalin	(Mangliket al., 2016)
SR-17018	Hot plate – mouse	C57/BL6J	52 °C, 20 s	(Grim et al., 2020; Schmid et al., 2017)
		C57/BL6	54 °C, 20 s	(Gillis, Gondin, et al., 2020)
	Tail flick – mouse	C57/BL6J	49 °C, 30 s	(Grim et al., 2020; Schmid et al., 2017)
Mitragynine	Tail flick – mouse	CD-1	Variable, 3× baseline	(Varadi et al., 2016)
		C57/BL6	Variable, 3× baseline
		C57/BL6J	48 °C, 30 s	(Wilson et al., 2021)
		129S1	Variable, 10 s	(Kruegel et al., 2019)
7-OH Mitragynine	Tail flick – mouse	CD-1	Variable, 3× baseline	(Varadi et al., 2016)
		129S1	Variable, 10 s	(Kruegel et al., 2019)
Mitragynine Pseudoindoxyl	Hot plate – mouse	CD-1	55 °C, 30 s	(Varadi et al., 2016)
	Tail flick – mouse	CD-1	Variable, 3× baseline	(Varadi et al., 2016), (Wilson et al., 2021)
		C57/BL6	Variable, 3× baseline
		129Sv6	Variable, 3× baseline
		C57/BL6J	48 °C, 30 s
Tianeptine	Hot plate – mouse	C57/BL6	50 or 55 °C, 30 s	(Samuels et al., 2017)
MP-1208 & MP1207	Tail flick – mouse	C57BL/6	55 °C,15 s	(Uprety et al., 2021)
CYM51010	Tail flick – mouse	C57/BL6	Heat intensity	(Gomes et al., 2013)
			10 (IITC LifeScience), 20 s	(Faouzi et al., 2020)
		C57/BL6	Variable, 10 s
		CD-1	Variable, 10 s
		129	Variable, 10 s
MP135	Tail flick – mouse	C57/BL6	Variable, 10 s	(Faouzi et al., 2020)
		CD-1	Variable, 10 s
		129	Variable, 10 s
	Hargreaves – rat	Long Evans	not given
AT-201	Tail flick – mouse	ICR	Radial beam	(Khroyan et al., 2007; Toll et al., 2009)
			(Stoelting, Wood Day, IL), 15 s
Endomorphin analogues	Tail flick – mouse	CD-1	Variable, 9 s	(Zadina et al., 2016)
	Tail flick – rat	Sprague-Dawley	Variable, 9 s

Summary of the antinociception assay, species, strain and cut-offs used for the evaluation of novel opioids.