Increased synaptic markers in hippocampus of depressed patients.

The neuronal adhesion molecule, D2-protein, and the marker for mature synapses, D3-protein, were studied by crossed immunoelectrophoresis in postmortem samples of human brain hippocampus and frontal cortex. The samples were obtained from 6 patients with endogenous depression, 6 patients with Parkinson's disease, and 9 controls without known neurological or psychiatric disorders. Both D2-protein and D3-protein were significantly increased in hippocampus of depressed patients compared to controls (32% and 30%, respectively) and compared to Parkinson's disease patients (31% and 24%, respectively). However, no significant change was observed in frontal cortex. Combined with the previously observed increase in the level of D2-like protein in blood plasma from depressed patients the findings may indicate that, at least in some regions of the brain, synaptic turnover is increased during depression.