Serene Science GABA Calm from Source Naturals features two inhibitory neurotransmitters, GABA and glycine combined with N-acetyl L-tyrosine, a precursor to norepinephrine and dopamine. GABA (gamma-aminobutyric acid) is an amino acid derivative and a key inhibitory neurotransmitter. Neurotransmitters are chemical messengers that carry information between nerve cells or from nerve cells to other target cells. GABA is synthesized directly from glutamic acid. It has an inhibitory effect on the firing of neurons and supports a calm mood. In addition, taurine supports the calming effects of GABA.  The lozenge form dissolves in the mouth for quick and convenient delivery.