Adrenergic stimulation decreases osteoblast oxytocin synthesis

Oxytocin (OT) regulates bone mass by inducing the differentiation of osteoblasts to a mature, mineralizing phenotype. We have shown recently that osteoblasts can synthesize OT. In view of known interactions between OT-ergic and adrenergic neurons in the central nervous system, we questioned whether the negative regulation of osteoblast differentiation by adrenergic nerves was mediated through its suppression of OT synthesis. We first confirmed that α_1b and β₂ adrenergic receptors were expressed on both primary murine osteoblasts and MC3T3-E1 cells. We then showed that α₁ and β₂ adrenergic agonists downregulated OT synthesis, and that the effect of each agonist was reversed by its respective antagonist. The data suggest that the negative effects of adrenergic stimulation on bone mass could, in part, arise from decreased OT synthesis.