Abstract
PurposeTo evaluate the feasibility of spectral editing for quantification of γ‐aminobutyric acid (GABA) in the rat brain and to determine whether altered GABA concentration in the ventral striatum is a neural endophenotype associated with trait‐like impulsive behavior.Materials and MethodsSpectra were acquired at 4.7T for 23 male Lister‐hooded rats that had been previously screened for extremely low and high impulsivity phenotypes on an automated behavioral task (n = 11 low‐impulsive; n = 12 high‐impulsive). Voxels of 3 × 7 × 4 mm3 (84 μL) centered bilaterally across the ventral striatum were used to evaluate GABA concentration ratios.ResultsQuantifiable GABA signals in the ventral striatum were obtained for all rats. Mean‐edited GABA to n‐acetyl aspartate (NAA) ratios in the ventral striatum were 0.22 (95% confidence interval [CI] [0.18, 0.25]). Mean GABA/NAA ratios in this region were significantly decreased by 28% in high‐impulsive rats compared to low‐impulsive rats (P = 0.02; 95% CI [–53%, –2%]).ConclusionThese findings demonstrate that spectral editing at 4.7T is a feasible method to assess in vivo GABA concentrations in the rat brain. The results show that diminished GABA content in the ventral striatum may be a neural endophenotype associated with impulsivity. J. Magn. Reson. Imaging 2016;43:1308–1312.
Highlights
To evaluate the feasibility of spectral editing for quantification of c-aminobutyric acid (GABA) in the rat brain and to determine whether altered Gamma-aminobutyric acid (GABA) concentration in the ventral striatum is a neural endophenotype associated with trait-like impulsive behavior
MEGA-PRESS spectra obtained were of high quality from each rat, showing the feasibility of the method in rats at 4.7T
We chose n-acetyl aspartate (NAA) to normalize the GABA signal for the least error, as it has the strongest signal in the water-suppressed spectra
Summary
To evaluate the feasibility of spectral editing for quantification of c-aminobutyric acid (GABA) in the rat brain and to determine whether altered GABA concentration in the ventral striatum is a neural endophenotype associated with trait-like impulsive behavior. Conclusion: These findings demonstrate that spectral editing at 4.7T is a feasible method to assess in vivo GABA concentrations in the rat brain. Efforts to measure GABA in vivo have included short echo time sequences, 2D J-resolved spectroscopy, and spectral editing sequences, the most widely used of which is MescherGarwood point-resolved spectroscopy, or MEGA-PRESS.[5,6] The 1H spectrum of GABA (H3N-CH2-CH2-CH2-COO-) has three multiplets at 1.9 ppm, 2.3 ppm, and 3.0 ppm, which overlap with n-acetylaspartate (NAA), glutamine/glutamate, and creatine, respectively. The present study investigated the feasibility and utility of MEGA-PRESS at 4.7T for resolving regional GABA content in the rat brain
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