Gamma-aminobutyric acid (GABA) peak

Gamma-aminobutyric acid (GABA) is the principle inhibitory neurotransmitter in the central nervous system  and as such, is one of the compounds examined in MR spectroscopy.  It is present in the human brain at a concentration of about 1 mM, a whole order of magnitude lower than some of the more abundantly present metabolites. GABA resonates at approximately 2.2-2.4 ppm chemical shift, overlapping the peaks of the more abundant metabolites N-acetylaspartate (NAA), creatine (Cr), and glutamate-glutamine (Glx) . Therefore, it is not routinely possible to separate it from the other peaks in this region of the spectrum.

Changes in concentration of GABA have been reported in a number of clinical scenarios, although day-to-day application is limited :

• decreased
  • epilepsy: decreased with recent seizures
  • stiff person syndrome
    • major depressive disorder and bipolar disorder
  • schizophrenia
  • chronic primary insomnia
  • autism