Glutamate (neurotransmitter)
In neuroscience, glutamate refers to the anion of glutamic acid in its role as a neurotransmitter: a chemical that nerve cells use to send signals to other cells. It is by a wide margin the most abundant excitatory neurotransmitter in the vertebrate nervous system. It is used by every major excitatory function in the vertebrate brain, accounting in total for well over 90% of the synaptic connections in the human brain. It also serves as the primary neurotransmitter for some localized brain regions, such as cerebellum granule cells.
Arvid Carlsson
In 1957 Kathleen Montagu demonstrated the presence of dopamine in the human brain; later that same year Carlsson also demonstrated that dopamine was a neurotransmitter in the brain and not just a precursor for norepinephrine. Carlsson went on to develop a method for measuring the amount of dopamine in brain tissues. He found that dopamine levels in the basal ganglia, a brain area important for movement, were particularly high. He then showed that giving animals the drug reserpine caused a decrease in dopamine levels and a loss of movement control. These effects were similar to the symptoms of Parkinson's disease. By administering to these animals L-Dopa, which is the precursor of dopamine, he could alleviate the symptoms. These findings led other doctors to try using L-Dopa in patients with Parkinson's disease, and it was found to alleviate some of the symptoms in the early stages of the disease. L-Dopa is still the basis for most commonly used means of treating Parkinson's disease.