Microglia morphology in the developing primate amygdala and effects of early life stress.

The paralaminar (PL) nucleus of the amygdala is an important source of plasticity, due to its unique repository of immature glutamatergic neurons. PL immature neurons mature between birth and adolescence. This process is likely supported by synaptogenesis, which requires microglia. Between infancy and adolescence in macaques, PL microglia became more dense, and shifted to a 'ramified' phenotype, consistent with increased synaptic pruning functions. Early life stress in the form of maternal separation, however, blunted this normal trajectory, leading to persistent 'parainflammatory' microglial morphologies. We speculate that early life stress may alter PL neuronal maturation and synapse formation through microglia.