Dopamine - Links To Psychosis

Links To Psychosis

Abnormally high dopaminergic transmission has been linked to psychosis and schizophrenia. However, clinical studies relating schizophrenia to brain dopamine metabolism have ranged from controversial to negative, with HVA levels in the CSF the same for schizophrenics and controls. Increased dopaminergic functional activity, specifically in the mesolimbic pathway, is found in schizophrenic individuals. However, decreased activity in another dopaminergic pathway, the mesocortical pathway, may also be involved. The two pathways are thought to be responsible for differing sets of symptoms seen in schizophrenia.

Antipsychotic medications act largely as dopamine antagonists, inhibiting dopamine at the receptor level, and thereby blocking the effects of the neurochemical in a dose-dependant manner. The older, so-called typical antipsychotics most commonly act on D2 receptors, while the atypical drugs also act on D1, D3 and D4 receptors, though they have a lower affinity for dopamine receptors in general. The finding that drugs such as amphetamines, methamphetamine and cocaine, which can increase dopamine levels by more than tenfold, can temporarily cause psychosis, provides further evidence for this link. However, many non-dopaminergic drugs can induce acute and chronic psychosis. The NMDA antagonists Ketamine and PCP both are used in research to reproduce the positive and negative symptoms commonly associated with schizophrenia.