Which neurotransmitter is synthesized from glutamate?

The neurotransmitter that is synthesized from glutamate is GABA (gamma-aminobutyric acid). Glutamate serves as the primary excitatory neurotransmitter in the brain, and through a process of decarboxylation, it is converted into GABA, which acts as the main inhibitory neurotransmitter. This conversion is facilitated by the enzyme glutamic acid decarboxylase (GAD).

GABA plays a crucial role in reducing neuronal excitability throughout the nervous system, helping to maintain balance between neuronal excitation and inhibition. In this context, it's important to understand that other neurotransmitters, such as dopamine, serotonin, and norepinephrine, have distinct biosynthetic pathways that do not involve glutamate as a precursor. For instance, dopamine is synthesized from the amino acid tyrosine, serotonin from tryptophan, and norepinephrine from dopamine, not from glutamate. Thus, GABA is uniquely linked to glutamate metabolism, making it the correct answer in this scenario.