Argon treatment alters microglial activation and neuronal cell death after experimental subarachnoid hemorrhage – a randomized controlled animal trial

Abstract Background Here, we demonstrate argon´s neuroprotective and immunomodulatory properties after experimental subarachnoid hemorrhage (SAH) examining various localizations (hippocampal and cortical regions) with respect to neuronal damage and microglial activation 6, 24 and 72h after SAH. Methods One hour after SAH (endovascular perforation rat model) or sham surgery, a gas mixture containing 50 vol% argon (argon group) or 50 vol% nitrogen (control group) was applied for 1h. Cerebral coronal sections (H&E; Iba-1 stained) were analyzed for neuronal cell death and microglial activation in predefined anatomical regions. Results Comparing the hippocampal regions 6h after SAH reduced neuronal damage was seen in the argon group (p<0.0001) as well as in the cortical region (p=0.014). Over time the effect diminished: A substantial difference 24h after SAH was only seen for the cortical region (p=0.004). No significant difference was observed 72h after SAH. The hippocampal and overall microglial activation 24h after SAH were significantly reduced in the argon group (p=0.013; p<0.0001), whereas 72h after SAH significance was only detected in the cortical area (p=0.014). Conclusion Argon treatment ameliorated early neuronal damage after SAH. However, inhibition of microglial activation might indicate a beneficial effect with regard to secondary inflammatory.