1 Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.
2 Department of Chemistry, University of Waterloo, 200 University Avenue, Waterloo, ON, N2L 3G1, Canada.
3 Current address: Restek Corporation, Bellefonte, PA, 16823, USA.
4 Current address: Department of Pharmacodynamics and Molecular Pharmacology, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Bydgoszcz, Poland.
5 Neuroimaging Research Section, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, M5T 1R8, Canada.
6 Harquail Centre for Neuromodulation, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, 2075, Bayview Avenue, Toronto, ON, M4N 3M5, Canada.

Oxylipins are key lipid mediators of important brain processes, including pain, sleep, oxidative stress, and inflammation. For the first time, an in-depth profile of up to 52 oxylipins can be obtained from the brains of awake moving animals using in vivo solid-phase microextraction (SPME) chemical biopsy tool in combination with liquid chromatography-high resolution mass spectrometry. Among these, 23 oxylipins are detectable in the majority of healthy wildtype samples. This new approach successfully eliminates the changes in oxylipin concentrations routinely observed during the analysis of post-mortem samples, allows time-course monitoring of their concentrations with high spatial resolution in specific brain regions of interest, and can be performed using the same experimental set-up as in vivo microdialysis (MD) thus providing a new and exciting tool in neuroscience and drug discovery.