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Environmental enrichment enhances the antidepressant effect of ketamine and ameliorates spatial memory deficits in adult rats.

Deren Aykan, Mert Genc, Gunes Unal

Pharmacology, Biochemistry, and Behavior July 1, 2024 DOI: 10.1016/j.pbb.2024.173790 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Randomized controlled trial Peer reviewed
Population Adult male Wistar rats
Interventions environmental enrichment ketamine
Dose 20 mg/kg, IP
Duration 50 days housing, including 13-day behavioral testing period
Topics Ketamine Esketamine
Keywords Behavioral despair C-fos Environmental enrichment Habenula Spatial memory Ketamine therapy Neuroscience research Depression treatment Behavioral neuroscience
Citations 8
Key findings Environmental enrichment combined with ketamine produced a synergistic antidepressant effect and ameliorated ketamine-induced spatial memory deficits in rats.

Abstract

Ketamine is a rapid-acting antidepressant associated with various cognitive side effects. To mitigate these side effects while enhancing efficacy, it can be co-administered with other antidepressants. In our study, we adopted a similar strategy by combining ketamine with environmental enrichment, a potent sensory-motor paradigm, in adult male Wistar rats. We divided the animals into four groups based on a combination of housing conditions and ketamine versus vehicle injections. The groups included those housed in standard cages or an enriched environment for 50 days, which encompassed a 13-day-long behavioral testing period. Each group received either two doses of ketamine (20 mg/kg, IP) or saline as a vehicle. We tested the animals in the novel object recognition test (NORT), forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and Morris water maze (MWM), which was followed by ex vivo c-Fos immunohistochemistry. We observed that combining environmental enrichment with ketamine led to a synergistic antidepressant effect. Environmental enrichment also ameliorated the spatial memory deficits caused by ketamine in the MWM. There was enhanced neuronal activity in the habenula of the enrichment only group following the probe trial of the MWM. In contrast, no differential activity was observed in enriched animals that received ketamine injections. The present study showed how environmental enrichment can enhance the antidepressant properties of ketamine while reducing some of its side effects, highlighting the potential of combining pharmacological and sensory-motor manipulations in the treatment of mood disorders.

Comparable studies

Other preclinical and animal studies on ketamine, most cited first.

Study Year Design Participants
mTOR-Dependent Synapse Formation Underlies the Rapid Antidepressant Effects of NMDA Antagonists Rats 2010 Observational study
Activation of Glutamatergic Neurotransmission by Ketamine: A Novel Step in the Pathway from NMDA Receptor Blockade to Dopaminergic and Cognitive Disruptions Associated with the Prefrontal Cortex Conscious rats 1997 Dose-response study with microdialysis and behavioral testing
NMDAR inhibition-independent antidepressant actions of ketamine metabolites Mice 2016 Preclinical study
The dissociative anaesthetics, ketamine and phencyclidine, selectively reduce excitation of central mammalian neurones by N‐methyl‐aspartate Spinal neurons in decerebrate or pentobarbitone-anaesthetized cats and rats 1983 Experimental study
R-ketamine: a rapid-onset and sustained antidepressant without psychotomimetic side effects Mice 2015 Experimental study

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Ketamine Esketamine