Isotope Dilution-Based Targeted and Nontargeted Carbonyl Neurosteroid/Steroid Profiling

In the 2018 study, researchers developed an isotope dilution-based targeted and nontargeted (ID-TNT) profiling method for carbonyl neurosteroids/steroids, which are brain-derived steroids involved in modulating neuronal excitability. This method, which includes stable isotope dilution, hydroxylamine derivatization, high-resolution mass spectrometry (MS) scanning, and data-dependent MS/MS analysis, allows for the absolute quantification of several neurosteroids, including pregnenolone and progesterone, and the relative quantification of other carbonyl-containing steroids. The method was validated using an acute stress mouse model and pharmacological manipulation with finasteride, revealing that brain levels of 3α,5α-tetrahydroprogesterone were higher than previously reported and that finasteride administration significantly increased brain pregnenolone. The study's findings suggest that this analytical approach is advantageous for investigating neurosteroid/steroid pathways and understanding their roles in brain function and disorders.