Hippocampal gene expression, serum cortisol level, and spatial memory in rats exposed to hypergravity

Area of Science:

• Neuroscience
• Space Biology
• Molecular Biology

Background:

• Altered gravity conditions, such as those experienced in space, can significantly impair spatial memory and navigation.
• The hippocampus, crucial for spatial memory, receives input from gravity-sensing otolith organs, highlighting its sensitivity to gravitational changes.

Purpose of the Study:

• To identify key molecules within the rat hippocampus involved in adapting spatial memory performance to altered gravity conditions.
• To investigate the molecular mechanisms underlying spatial memory deficits and adaptations under hypergravity stress.

Main Methods:

• Rats were exposed to two weeks of 2G hypergravity (HG).
• Hippocampal gene expression was analyzed using microarray and real-time PCR.
• Spatial memory was assessed using the radial arm maze test.
• Serum cortisol levels were measured to evaluate stress response.

Main Results:

• Rats exposed to HG showed significantly lower accuracy in the radial arm maze, indicating impaired spatial memory.
• Gene expression analysis revealed an upregulation of insulin-like growth factor binding protein 2 (IGFBP2) in the hippocampus.
• Serum cortisol levels normalized by the end of the HG exposure, suggesting adaptation to the stress.

Conclusions:

• The insulin-like growth factor (IGF) system, particularly IGFBP2, may play a role in the adaptation of spatial memory to altered gravity.
• Neurotrophic and synaptic plasticity mechanisms mediated by the IGF system could be involved in this adaptive process.