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The effect of orexin 1 and orexin 2 receptors antagonisms in the basolateral amygdala on memory processing in a
Motahareh Rouhi Ardeshiri1, Narges Hosseinmardi1, Esmaeil Akbari2
1Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Abstract:
There is an extensive evidence concerning basolateral amygdala (BLA) function to hippocampal memory processing. However, few researches have addressed the orexinergic system roles in this modulation. Then, the present study aims at investigating the action of orexin 1 and 2 receptors in BLA on passive avoidance (PA) learning. Wistar male rats (n=79) were trained to avoid foot shock in one type of PA task. The rats were injected bilaterally into BLA, a selective orexin 1 receptor antagonist, SB-334867-A (3, 6, 12μg/0.5μl), and an orexin 2 receptor antagonist, TCS-OX2-29 (2.5, 5, 10μg/0.5μl), after training or before retrieval of the inhibitory avoidance task. Control rats received dimethyl sulfoxide at the same volume. The amount of learning was assessed 24h later. The time of the first entrance to the dark compartment and the total time spending in the light compartment were measured as criteria for the avoidance memory. The results showed that consolidation and retrieval were significantly impaired by SB-334867-A administration into BLA in 3, 6 and 12μg/0.5μl. However, TCS-OX2-29 in 2.5μg/0.5μl could not influence neither consolidation nor retrieval. The TCS-OX2-29 administration into BLA impaired memory retrieval in 5 and 10μg/0/5μl but not the consolidation. It gives the impression that orexinergic system of the BLA plays an important role in regulation of memory processing and learning in the rats.
Insights
Orexin 1 and 2 receptors in the basolateral amygdala (BLA) modulate memory processing. Blocking orexin 1 receptors impaired passive avoidance learning consolidation and retrieval, while blocking orexin 2 receptors primarily affected retrieval.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Pharmacology
Background:
- The basolateral amygdala (BLA) is crucial for hippocampal memory processing.
- The role of the orexinergic system in BLA-mediated memory modulation is not well understood.
Purpose of the Study:
- To investigate the involvement of orexin 1 and 2 receptors in the BLA on passive avoidance (PA) learning in rats.
Main Methods:
- Wistar male rats were trained in a PA task.
- Selective orexin 1 receptor antagonist (SB-334867-A) and orexin 2 receptor antagonist (TCS-OX2-29) were bilaterally injected into the BLA.
- Memory consolidation and retrieval were assessed 24 hours post-training.
Main Results:
- SB-334867-A administration into the BLA significantly impaired both memory consolidation and retrieval.
- TCS-OX2-29 at lower doses (2.5μg/0.5μl) did not affect consolidation or retrieval.
- Higher doses of TCS-OX2-29 (5 and 10μg/0.5μl) impaired memory retrieval but not consolidation.
Conclusions:
- The orexinergic system within the BLA plays a significant role in regulating memory processing and learning.
- Orexin 1 receptors are involved in both memory consolidation and retrieval, while orexin 2 receptors are primarily involved in retrieval.
