Region-specific changes in ascorbate concentration during rat brain development quantified by in vivo (1)H NMR...

Ascorbate (vitamin C, Asc) was quantified in vivo using short-TE (1)H NMR spectra from a previously published study on regional and developmental changes in the neurochemical profile of the rat brain (Tkac I, Rao R, Georgieff MK, Gruetter R. Magn Reson Med. 2003; 50: 24-32). Asc concentration was quantified on postnatal days P7-P28 from three regions that are of interest in the study of neurocognitive development, i.e. the hippocampus, striatum and cerebral cortex. The previously measured (1)H NMR spectra were re-analyzed using LCModel with the Asc spectrum included in the basis set. The Asc concentration was consistently quantified from all 110 re-analyzed spectra with an estimated fitting error of 7% (i.e. the average Cramer-Rao lower bound). The sensitivity of Asc quantification was sufficiently high to detect regional and developmental changes in Asc concentration. The concentration of Asc was highest on P7, and decreased with age in all three brain regions (p < 0.001) in agreement with previous in vitro studies. At P10 and older postnatal ages, an inhomogeneous distribution of Asc among brain regions was detected. In addition to facilitating the quantification of this important antioxidant concentration, the inclusion of the Asc spectrum in the LCModel basis set improved the quantification accuracy of other brain metabolite concentrations in the neurochemical profile.