Cerebral blood flow and metabolic changes in hippocampal regions of a modified rat model with chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH) causes neurodegeneration which contributes to the cognitive impairment. This study utilized a modified rat model with CCH to investigate cerebral blood flow (CBF) and hippocampal metabolic changes. CBF was measured by laser Doppler flowmetry. Various metabolic ratios were evaluated from selective volumes of interest (VOI) in left hippocampal regions using in vivo proton magnetic resonance spectroscopy (1H-MRS). The ultrastructural changes with special respect to ribosomes in rat hippocampal CA1 neurons were studied by electron microscopy. CBF decreased immediately after CCH and remained reduced significantly at 1 day and 3 months postoperatively. 1H-MRS revealed that CCH led to a significant decrease of N-acetyl aspartate/creatine (NAA/Cr) ratio in the hippocampal VOI in the model rats compared with the sham-operated control rats. However, no changes of myo-inositol/Cr, choline/Cr and glutamate and glutamine/Cr ratios between the model and control groups were observed. Under electron microscopy, most rosette-shaped polyribosomes were relatively evenly distributed in the hippocampal CA1 neuronal cytoplasms of the control rats. After CCH, most ribosomes were clumped into large abnormal aggregates in the model rats. Our data suggests that both permanent decrease of CBF and reduction of NAA/Cr ratio in the hippocampal regions may be related to the cognitive deficits in rats with CCH.