Imbalance of the Gs and Gi/o function in post-mortem human brain of depressed patients.

The amounts of various G protein subunits in postmortem brain samples from the parietal and temporal cortices were the same in controls and depressive patients as demonstrated by immunoblotting. However, photoaffinity GTP labeling (AAGTP) of Gi/o alpha, but not Gs alpha, was significantly increased in depressives in both cortex regions. Furthermore, the ratio of Gs/Gi/o AAGTP incorporation revealed a significant reduction in depressives in these regions. The present findings suggest that an imbalance of second messengers via G protein function may be involved in the pathophysiology of depression.