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Effect of reversible inactivation of the reuniens nucleus on spatial learning and memory in rats using Morris water
Farzaneh Ghiafeh Davoodi1, Fereshteh Motamedi, Nasser Naghdi
1Neuroscience Research Center and Department of Physiology, Faculty of medicine, Shahid Beheshti University (Medical Sciences), Tehran, Iran.
Abstract:
The involvement of thalamic midline nuclei (MLN) in early stage of Alzheimer's disease and in diencephalic amnesia has drawn attention to the connectivity between the nucleus reuniens (RE) and structures of medial temporal lobe. RE is major source of thalamic afferents to the hippocampus and has been shown to exert powerful excitatory action on CA1 of hippocampus, which is supposed to be involved in learning and memory processes. However, the role of the RE on spatial memory is a controversial issue. The present study was designed to evaluate the role of the RE in acquisition, consolidation and retrieval of spatial reference memory (RM) and working memory (WM). We assessed the effect of reversible inactivation of RE with tetracaine (0.5 microl, 2%) on different stages of memory. Rats were trained on RM and WM versions of the Morris water maze (MWM) task. RE was inactivated before or immediately after training or before the probe trial of retrieval tests. The data showed that reversible inactivation of the RE significantly impaired both RM and WM versions of MWM. Therefore, it seems that nucleus reuniens of thalamus plays a role in spatial RM and WM version of the MWM task in rats.
Insights
The nucleus reuniens (RE) in the thalamus is crucial for spatial memory. Inactivating the RE impaired rats' ability to learn and recall spatial reference and working memory tasks.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Memory Research
Background:
- Thalamic midline nuclei (MLN), particularly the nucleus reuniens (RE), are implicated in Alzheimer's disease and amnesia.
- The RE connects to the medial temporal lobe and hippocampus, influencing learning and memory processes.
- The specific role of the RE in spatial memory remains debated.
Purpose of the Study:
- To investigate the role of the nucleus reuniens (RE) in the acquisition, consolidation, and retrieval of spatial reference memory (RM) and working memory (WM).
Main Methods:
- Reversible inactivation of the RE using tetracaine in rats.
- Assessment of memory performance using the Morris water maze (MWM) task for both RM and WM.
- Inactivation occurred before training, after training, or before retrieval tests.
Main Results:
- Reversible inactivation of the RE significantly impaired performance in both spatial reference memory and working memory versions of the MWM task.
- These impairments were observed across different stages of memory processing (acquisition, consolidation, retrieval).
Conclusions:
- The nucleus reuniens plays a significant role in both spatial reference memory and working memory as assessed by the MWM task in rats.
- These findings highlight the importance of thalamic nuclei in complex cognitive functions like spatial navigation and memory.
