Table 1.

List of modulatory compounds or drugs utilized in this study.

Drug	Concentrations tested	Dosing unit	Solvent	Product Information	Suggested Working Conc. from literature	Reference	system
DAMGO	0.5~70 μM	0.5 μM, 5 μM	5 mM in Medium	Sigma (Cat E7380)	5 μM	[72]	Rat, preBötC brain
					0.2 μM, 0.5 μM, 1 μM	[10, 93]	Rat, preBötC brain slice
Naloxone	1~240 μM	1 μM, 10 μM, 100 μM	100 mM in DMSO, further diluted in medium	Sigma (USP 1453005)	100 μM	[72]	Rat, preBötC brain
					10 μM	[10]	Rat, preBötC brain
					0.5mM	[94]	Decerebrated dogs
Codeine Hydrochloride	1~100 μM	1 μM, 10 μM	10 mM in H2O, further diluted in medium	NIDA 9050-001	1~100 μM	[91]	In vitro competitive binding assay
Methadone Hydrochloride	10 ~1000 nM	20 nM, 200 nM, 2000 nM	20 mM in H2O, further diluted in medium	NIDA 9250-003	1~1000 nM	[91]	In vitro competitive binding assay
Fentanyl Hydrochloride	0.02 ~ 600 nM	0.02 nM, 0.2 nM, 2 nM, 20 nM, 200 nM	10 mM in H2O, further diluted in medium	NIDA 9801-001	0.1~100 nM	[72, 91, 93]	Rat preBötC brain slice; in vivo CSF perfusion; In vitro competitive binding assay
SST	1 μM	1 μM	0.1 mM in Medium	Sigma (S9129)	1 μM	[80]	Mice, preBötC brain slice
Substance P	5 μM	5 μM	0.5 mM in Medium	R&D (1156/5)	1 μM	[79]	Mice, preBötC brain slice
ATP	100 μM	100 μM	10 mM in Medium	Sigma (A2383)	100 μM	[73]	Rat, preBötC brain slice