Abstract
Formation of episodic memories (i.e. remembered experiences) requires a process called consolidation which involves communication between the neocortex and hippocampus. However, the neuromodulatory mechanisms underlying this neocortico-hippocampal communication are poorly understood. Here, we examined the involvement of dopamine D1 receptors (D1R) and D2 receptors (D2R) mediated signaling on memory consolidation using the Novel Object Recognition (NOR) test. We conducted the tests in male Hartley guinea pigs and cognitive behaviors were assessed in customized Phenotyper home cages utilizing Ethovision XT software from Noldus enabled for the 3-point detection system (nose, center of the body, and rear). We found that acute intraperitoneal injections of either 0.25 mg/kg SCH23390 to block D1Rs or 1.0 mg/kg sulpiride to block D2Rs soon after acquisition (which involved familiarization to two similar objects) attenuated subsequent discrimination for novel objects when tested after 5-hours in the NOR test. By contrast guinea pigs treated with saline showed robust discrimination for novel objects indicating normal operational processes undergirding memory consolidation. The data suggests that involvement of dopaminergic signaling is a key post-acquisition factor in modulating memory consolidation in guinea pigs.
Highlights
In humans memory is defined as the ability to acquire, store, and retrieve information
The current study investigated the involvement of dopaminergic signaling on memory consolidation after learning using the novel object recognition (NOR) test in the guinea pig animal model
We have successfully utilized the guinea pig animal model to assess the involvement of D1 receptors (D1R) and D2 receptors (D2R) mediated signaling on object recognition memory consolidation
Summary
In humans memory is defined as the ability to acquire, store, and retrieve information. Several different types of long-term memory (LTM) have been distinguished, including declarative and non-declarative memory. Declarative memory is further subdivided into episodic memory (i.e. experiences and events) and semantic memory (i.e. facts, meanings, and concepts) which both require conscious recall. Episodic memory is the term given to the capacity to recall or ‘remember’ experienced events and situations [1]. Once thought to be unique to humans, it is clear that the core behavioral properties of episodic memory are present across mammals as well as other animal species [2]; the major brain regions responsible for PLOS ONE | DOI:10.1371/journal.pone.0135578. Once thought to be unique to humans, it is clear that the core behavioral properties of episodic memory are present across mammals as well as other animal species [2]; the major brain regions responsible for PLOS ONE | DOI:10.1371/journal.pone.0135578 August 14, 2015
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