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.