# Astrocyte Activation in the Hippocampus Following Cardiopulmonary Bypass in a Rat Model: A Pilot Study

## TL;DR

This study shows that cardiopulmonary bypass in rats activates astrocytes in the hippocampus, suggesting a link to post-surgery delirium.

## Contribution

This is the first study to demonstrate astrocyte activation in the hippocampus following cardiopulmonary bypass in a rat model.

## Key findings

- Astrocyte activation was observed in the hippocampal CA3 region after cardiopulmonary bypass.
- GFAP-positive astrocyte area density was significantly higher in the CPB group compared to the sham group (p=0.047).

## Abstract

Background: Delirium after cardiac surgery is associated with poor outcomes. Cardiopulmonary bypass (CPB) increases blood-brain barrier (BBB) permeability and neuroinflammation, contributing to delirium. While microglial activation after CPB has been reported, the role of astrocytes remains unclear. This study aimed to determine whether astrocytes are activated in the hippocampus after CPB in a rat model.

Methods: Male Sprague-Dawley rats (13-15 weeks, 400-450 g) were anesthetized, mechanically ventilated, and randomized to sham (n=4) or CPB (n=4). CPB was performed with a primed circuit using a membrane oxygenator at 150 mL/kg/min for 60 min. Immunofluorescence and immunohistochemistry were performed to assess inflammatory markers and glial fibrillary acidic protein (GFAP) expression. GFAP-positive area density in the hippocampus was quantified, and groups were compared using the Mann-Whitney U test (p<0.05).

Results: GFAP immunofluorescence demonstrated increased astrocyte activation in the hippocampal CA3 region after CPB. Area density of GFAP-positive astrocytes was significantly higher in the CPB group than in the sham group (p=0.047).

Conclusion: CPB induced astrocyte activation in the hippocampal CA3 region. These findings indicate that CPB induces astrocyte activation in the hippocampus, consistent with a neuroinflammatory response.