Table 1.

Effect of Exon-specific Knockouts of MOR-1 on μ Opioid Analgesia

	Exon-1 (mg/kg, s.c.)			Exon-11 (mg/kg, s.c.)
Drug	WT	KO	Shift	WT	KO	Shift
Morphine	5.0	>100	>20	1.6	2.6	1.6
M6G	3.8	8.5	2.3	0.92	19.3	21
Heroin	1.2	4.0	2.7	0.58	3.2	5.5
Fentanyl				0.024	0.230	9.7

ED₅₀ values (mg/kg, s.c.) were determined from dose-response curves in groups of animals for the exon-1 knockout studies³⁴ and the exon-11 knockout studies.³⁶