Table 2.

Knockout mice models and memory performance.

Behavioral task	Knockout type	Effect on memory	Reference(s)
Water maze*	Hdc −/−	↓	[111]
Water maze	Hdc −/−	↑	[112]
Object recognition*	Hdc −/−	Unaffected	[111]
Nonreinforced episodic object memory	Hdc −/−	↓	[112]
Contextual fear conditioning	Hdc −/−	↑	[113]
One-trial passive avoidance	Hdc −/−	↑	[111]
Open field (habituation)	Hdc −/−	Unaffected	[114]
Inhibitory avoidance	KO H1−/−	Unaffected	[115]
Conditioned place preference	KO H1−/−	↓	[116]
Radial-maze task	KO H1−/−	↓	[117]
Auditory and contextual fear conditioning	KO H1−/−	↑	[68]
Auditory and contextual fear conditioning	KO H2−/−	↑	[68]
Object recognition	KO H1−/−	↓	[68]
Object recognition	KO H2−/−	↓	[68]
Barnes maze	KO H1−/−	↓	[68]
Barnes maze	KO H2−/−	↓	[68]
Barnes maze	KO H3−/−	↑	[118]
Motoric long-term memory	KO H1−/−	↓	[119]
Episodic and procedural memory	KO H1−/−	↓	[119]

*This work was done using female mice.

Hdc: histidine decarboxylase.

H1, H2, H3: histaminergic receptor type.