Probing impact of sleep deprivation on hippocampal neurochemistry in rats using CEST imaging and H-MRS at 7.0T MRI.

Purpose: Sleep is a physiological process that plays a crucial role in maintaining cognitive functions. The hippocampus, a key brain region implicated in cognition, is particularly sensitive to sleep deprivation. we aim to investigate impact of sleep deprivation on hippocampal neurochemistry in rats using CEST imaging and H-MRS.

Methods: Twelve female Sprague-Dawley rats were randomly divided into sleep deprivation and control groups. All rats experienced Morris water maze training and testing from Day 1 to Day 6 and underwent MRI scans including CEST imaging and H-MRS on Days 1 and Day 3. Lastly, rats were euthanized for Nissl staining.

Results: Sleep deprivation led to a significant decrease in CEST signals across various frequency offsets (0.5-3.5 ppm) in the hippocampus (P < 0.05). Meanwhile, sleep deprivation caused an increase in glutamate (P < 0.0001) with no alterations in other metabolites (P > 0.05). Behaviorally, sleep deprivation impaired learning-memory abilities, evidenced by reduced target quadrant distance (P < 0.001) and time (P < 0.01) in the Morris water maze. Histologically, sleep deprivation caused a decline of surviving neurons in the hippocampal CA1 and CA3 regions (P < 0.001). These indicators correlated negatively with the concentrations of glutamate (P < 0.05) and positively with most of the CEST signals (P < 0.05) in the hippocampus.

Conclusion: The integration of CEST imaging and H-MRS offers a promising approach for identifying imaging biomarkers that aid in the assessment and management of sleep deprivation's impact on hippocampal neurochemistry.