This, in turn, increases brain-derived neurotrophic factor (BDNF) synthesis, and through the activation of both mammalian target of rapamycine (mTOR) and alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) receptors, leads to rapid increases in dendritic spine density in the cortical pyramidal cells specifically affected by chronic stress and hypercortisolemia.