GABA has two main absorption peaks at 12.2 and 16.8 in the Terahertz range.

γ-Aminobutyric acid (GABA) is an inhibitory neurotransmitter in the vertebrate central nervous system and plays a fundamental role in the balance between neuronal excitation and inhibition; the imbalance between excitation and inhibition can lead to coma, depression, convulsions, anxiety, restlessness, and insomnia.1–4 GABA has modulatory effects on enteric neurons and immune cells. Changes in GABA metabolism may be associated with the origin and spread of seizure activity. Furthermore, the pharmaceutical use of GABA in the treatment of certain neurological disorders, such as Parkinson’s disease and epilepsy, has also been reported.

https://pubs.rsc.org/en/content/articlehtml/2019/ra/c9ra02971k