71. Elevated dopamine-induced Gs protein measures in patients with schizophrenia

Heterotrimeric G proteins play a pivotal role in post-receptor information transduction and were previously implicated in the pathophysiology and treatment of mood disorders. Changes previously detected in G protein levels in postmortem brains of patients with schizophrenia could reflect effects of antipsychotic medication. The present study aims at quantitatively and functionally evaluating receptor-coupled G proteins in mononuclear leukocytes obtained from 23 untreated patients with schizophrenia and 30 healthy subjects, in an attempt to unravel a pattern of G protein measures in schizophrenia distinctive from patterns previously described in mood disorders. Dopamine-enhanced guanine nucleotide binding capacity to Gs protein through D1/5 receptor in mononuclear leukocytes of untreated patients with schizophrenia was significantly increased in comparison with healthy subjects. b-adrenergic and muscarinic receptor-coupled G protein functions, as well as Gsa, Gia and Gb immunoreactivities were similar to healthy subjects. These findings, distinctive for schizophrenia, unrelated to drug treatment, and differential from previous findings in mania and depression, may potentially help to differentiate between the major psychoses: schizophrenia vs. manicdepressive illness after the first psychotic episode.