Amygdalar expression of proteins associated with neuroplasticity in major depression and suicide

Doublecortin (DCX) and polysialilated neural cell adhesion molecule (PSA-NCAM), two proteins associated with immature neuronal phenotypes and elevated neuroplasticity in the adult brain, have recently been identified in the mammalian amygdala, and evidence from rodent studies suggests that stress may modify their expression in this brain region. The purpose of the present study was to investigate whether the expression of proteins involved in neuroplasticity is altered in the amygdala of individuals with depression.

Basolateral amygdala (BLA) and central amygdala (CeA) postmortem human brain samples were collected from individuals with a history of depression (n = 22 and 25, respectively) and psychiatrically healthy controls (CTRL; n = 14). Proteins associated with neuroplasticity were quantified using Western blotting.

Immunoblots revealed that depressed subjects displayed increased expression of DCX (p = 0.033) and PSA-NCAM (p = 0.027) in the BLA as compared to CTRLs. Subsequent analyses revealed that this effect was due primarily to a subset of depressed subjects who had not died by suicide (DNS). DNS subjects displayed higher DCX than CTRLs (p < 0.001) and depressed suicides (p = 0.001), and higher PSA-NCAM than CTRLs (p = 0.007). Conversely, within the CeA, DNS subjects displayed a tendency toward lower DCX expression than CTRLs (p = 0.062), and higher BDNF levels than DS subjects (p = 0.045).

These results suggest that the BLA and CeA display contrasting patterns of neuroplasticity in depression, and that greater impairment of amygdalar neuroplasticity may be associated with increased risk of suicide.