Sympathetic Nervous System and Hematopoiesis. Sympathetic nerves innervate the bone marrow and release neurotransmitters such as norepinephrine (NE) that is taken up by adrenergic receptors (AR) of the “niche” cells that make up the microenvironment of the hematopoietic stem cell (HSC). Niche cells include nestin and CXCL12 positive cells and endothelial cells (EC).