Since you have not specified wether the animal still lives I assume that is not the case:

You could measure 8-oxo-dG using an EIA/ELISA assay on DNA extracts or immunohistochemistry on fixed tissue slides. The EIA is very sensitive (and expensive), the immunohistochem. not really quantitative...

Or you could use the OxyDNA Kit from Argutus which also detects 8-oxo-dG. It works on whole cells and needs to be analyzed by flow cytometry or fluorescence microscopy. It could give nice indications areas with different stress levels when used on living, permeabilized brain slices.

All these assays measure formation of oxidized DNA adducts.

If you have living brain slices you could try a ROS-sensitive dye like H2DCFDA or Amplex Red, this would yield the actual ROS levels.

However, no method is actually very convenient... 8-oxo-dG is formed by air oxydation of DNA alone, so an environment with reduced O2 levels is advisable, otherwise you will get a high baseline.

H2DCFDA is not very specific, some peroxidases may oxidize it it regardsless of the presence of ROS. And it is very light sensitive...

Even less convenient methods would be HPLC-EC or HPLC-MS for 8-oxo-dG (lot of DNA needed) or oxidized lipids/proteins. Needs a MS specialist to perform these measurements.

If the animal still lives:

http://stroke.ahajournals.org/content/27/2/327.full

Good luck...

USE the method that Collins et al 2007 CELL ... its awesome!

Do you have an exact reference?

Kohanski, M. A., D. J. Dwyer, et al. (2007). "A Common Mechanism of Cellular Death Induced by Bactericidal Antibiotics." Cell 130(5): 797-810