G proteins as a biochemical tool for diagnosis and monitoring treatments of mental disorders.
ABSTRACT There is a significant gap between advances in medication for mental disorders and the present static situation of diagnosis and monitoring treatments of these disorders. Heterotrimeric G proteins play a pivotal role in postreceptor information transduction. These proteins were previously implicated by us in the biochemical mechanism underlying lithium action, and in the pathophysiology of mood disorders. We aimed at quantitatively and functionally evaluating G proteins in patients with major mental disorders in an attempt to unravel a differential pattern of G protein measures characterizing each disorder. We undertook G protein functional measurements coupled to beta-adrenergic, muscarinic or dopamine receptors through bacterial toxin-sensitive, agonist-enhanced [3H]-Gpp(NH)p binding capacity, substituted by quantitative measures of G alpha s, G alpha i, and G beta subunit proteins through immunoblot analysis using polyclonal anti-G submit antibodies in mononuclear leukocytes obtained from patients with major mental disorders in comparison with healthy volunteers. A differential pattern of receptor coupled G protein function and of their immunoreactive levels were detected in mononuclear leukocytes of patient s for the following mental disorders: mania, depression, schizophrenia, and panic. Normalization of altered G protein measures in mood-disorder ed patients occurred under specific treatments. As state-dependent markers, G protein measures can potentially be used as an aid in both the biochemical diagnosis of mental disorders and in the biochemical monitoring of the response to a specific treatment.