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Investigating the role of ventral hippocampal and medial septal dopamine receptors in social memory formation in rats
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Sana M. Barghi   , Ziagull Ibrahimi , Mahmoud Rezae , Mahsa Ahmadi , Javad Mirnajafi-Zadeh , Amir Shojaei |
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Abstract: (474 Views) |
Introduction: Episodic memory, which is dependent on the hippocampus, is known as social memory and it plays a crucial role in the survival of animals. The ventral tegmental area (VTA) plays an important role in the formation of this type of memory. This area plays a crucial role in regulating the activity of neurons in the hippocampus. It does this by sending direct dopaminergic fibers to the ventral hippocampus or by projecting such fibers to the medial septum (MS). In this study, the involvement of these two pathways in social memory formation was investigated.
Methods and Materials: Adult male rats underwent stereotaxic implantation of electrodes in the ventral hippocampus (vHip), medial prefrontal cortex (mPFC), and VTA in the right hemisphere to record local field potentials. In the MS group, a guide cannula was placed in the MS, and in the vHip group, a guide cannula was implanted into the vHip. After the recovery period, the MS group of animals received haloperidol (100 nM, 0.5 μL) in the MS, and the vHip group received this antagonist in vHip. Immediately, animals were placed in a box and exposed to a novel conspecific for ten minutes to form social memory. Then, the animals were allowed to sleep for two hours to consolidate their memory. After this period, social memory was tested.
Results: Inhibition of dopamine receptors in MS (and not in the vHip) significantly reduced the recognition index, and prevented the increase in hippocampal theta power and its functional connectivity with mPFC and VTA during memory encoding. It also increased the occurrence of hippocampal ripples during NREM sleep.
Conclusion: The VTA's dopaminergic fiber projections to the MS have a significant impact on the formation of social memory. These fibers likely regulate hippocampal theta rhythm, which plays a crucial role in episodic memory encoding.
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| Keywords: social memory, ventral hippocampus, ventral tegmental area, medial septum, medial prefrontal cortex, dopamine receptors |
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Full-Text [PDF 316 kb]
(121 Downloads)
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Type of Study: Research |
Subject:
General
Received: 2023/11/24 | Accepted: 2023/08/23 | Published: 2023/08/23
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