One of the main theories about schizophrenia is that too much dopamine in the brain causes this mental illness. Support for this comes from the fact that many antipsychotic medications used to treat schizophrenia work by blocking dopamine receptors. While the overproduction of dopamine is in part responsible for some of the symptoms of schizophrenia, other endogenous chemicals such as glutamate, GABA, acetylcholine, and serotonin alterations are also involved.