TABLE 2

Effects of genetic deletion of β-endorphin, POMC, and MOP-r on alcohol-related behaviors

Subjects	Sex	Model	Effect	Reference
β-Endorphin KO	Male + female	[1] 2-Bottle choice (24 h, 7%);	[1] Increase (intake and preference);	Grisel et al. (1999)
β-Endorphin KO	Male + female	[2] 2-Bottle choice (24 h, 10%)	[2] No difference (intake or preference)	Grisel et al. (1999)
β-Endorphin KO	Male	[1] 2-Bottle choice (24 h, 10%);	[1] No difference (intake);	Grahame et al. (2000)
		[2] 2-Bottle choice (2 h, 10%);	[2] Increase (intake);
		[3] ADE	[3] Increase (intake)
β-Endorphin KO	Male, female	2-Bottle choice (24 h, 16%);	Decrease (intake and preference) with sex difference	Racz et al. (2008)
Tpit KO mice with pituitary-specific POMC deletion	Male, female	1-Bottle (4 h, 15%) in DID	No difference in intake or preference in either sex	Zhou et al. (2017c)
nPE KO mice with hypothalamic-specific POMC deletion	Male, female	[1] 1-Bottle (4 h, 7.5%–30%) in DID;	Decrease (intake and preference) in all three models, with sex difference	Zhou et al. (2017c)
		[2] 2-Bottle choice (24 h, every other day, 7.5%–30%) in IA;
		[3] ADE
MOP-r KO	Male	[1] 30-min Operant self-administration (10%);	[1] Decrease (intake);	Roberts et al. (2000)
MOP-r KO	Male	[2] 2-Bottle choice (24 h, 10%)	[2] Decrease (intake and preference)	Roberts et al. (2000)
MOP-r KO	Male, female	[1] 2-Bottle choice (24 h, 2%–32%);	[1] Decrease (intake) with sex difference;	Hall et al. (2001)
MOP-r KO	Male, female	[2] CPP	[2] Decrease	Hall et al. (2001)
MOP-r KO with striatum-specific deletion	Male	[1] 2-Bottle choice (24 h, 10%);	[1] Decrease (intake and preference);	Ben Hamida et al. (2018)
		[2] 2-Bottle choice (24 h, every other day, 10%) in IA;	[2] Decrease (intakeand preference);
		[3] CPP	[3] Decrease

KO, knockout; nPE, neuronal Pomc enhancers.