Schematic drawing of brain-bone marrow axis in chronic psychological stress conditions.

When brain is exposed to chronic PS (1), the information is mediated to bone marrow through adrenergic nerves (2). Bone marrow niche cells innervated with sympathetic nerves decrease the expression of SDF-1 through β₃-adrenergic receptor (3). CXCR4^high monocytes egress to peripheral circulation from the bone marrow by reduction of SDF-1 at the bone marrow niche (4). Neurons in the PVN express MCP-1 under chronic PS condition, then accelerate infiltration of CCR2⁺ bone marrow-derived microglia into PVN (5).