Hi CEDPHD, how are you? Gamma-aminobutyric acid is an amino acid and the chief inhibitory neurotransmitter in the central nervous system and the retinas of humans that regulates muscle tone and other functions. It is also chiefly an excitatory neurotransmitter. You may go through this link to know more about Gamma-aminobutyric acid - http://en.wikipedia.org/wiki/GABA
"Both sleep problems and anxiety disorders may result from problems with GABA, which helps neutralize the effects of glutamate, a brain chemical that causes excitement. When there is too little GABA, it causes those racing thoughts that characterize anxiety -- and keep you up at night" http://www.webmd.com/sleep-disorders/news/20030912/chemical-may-link-mood-sleep-problems. Hope you may find some useful information. Take care.