Spatial memory of rats was assessed by Barnes Maze test to determine whether long-term neuroinflammation in a rat model of cardiac arrest caused memory and cognitive impairment

Title: Positron emission tomography imaging of long-term expression of the 18 kDa translocator protein after sudden cardiac arrest in rats

Journal: SHOCK (2021) 55(5):620–629. Link: https://journals.lww.com/shockjournal/Fulltext/2021/05000/Positron_Emission_Tomography_Imaging_of_Long_Term.8.aspx

Comments: Neuroinflammation is mediated by cells that express the 18 kDa translocation protein (TSPO). The temporal progression of TSPO-expressing cells in a 6-month rat model of cardiac arrest can be determined using longitudinal in vivo positron emission tomography (PET) imaging and the TSPO-specific tracer [18F] DAA1106. However, it is important to know whether long-term TSPO patterns following cardiac arrest affect spatial memory disorders. The researchers used Barnes Maze test to observe and analyze the rat model for up to 180 days to assess whether the rats suffered from such behaviors as spatial memory disorders.

Barnes Maze was established by using the characteristics of rats that like to be in the dark and inquisitive. Rats escaped from a bright and open platform through escape holes to a dark and narrow box under the platform. The Barnes Maze test was performed on Days 3, 13, 90, and 180. And researchers set “intervention types”: cardiac arrest group and sham operation group. Each rat was tested four times consecutively with an inter-trial delay of 15 minutes. In the first three tests, the spatial position of the escape box was the same. The spatial position of the escape box was changed in the fourth test (reversal test). The investigator recorded the time to find the escape hole and the time spent in the target quadrant (absolute search time D1-D4) for each of the four tests. For all postintervention trials, the time difference from baseline (relative search times ΔD1 to ΔD4) was calculated.The results showed that after intervention, there was no significant difference in absolute search time (D1-D4) between the cardiac arrest group and the sham operation group at any time point. However, compared with the sham-operated rats on the 14th day and the 18th day, the “ΔD2 in the target quadrant” of the rats with sudden cardiac arrest decreased significantly, indicating that it was difficult for the rats with sudden cardiac arrest to remember the position of the hole. The results of Barnes Maze test suggested that persistent neuroinflammation could affect spatial memory ability.