Single transcript level atlas of oxytocin and the oxytocin receptor in the mouse brain.

Oxytocin (OXT), a primitive nonapeptide known to regulate reproduction and social behaviors, is synthesized primarily in the hypothalamus and is secreted via the hypophyseal-portal system of the posterior pituitary gland. In line with the premise that pituitary hormones, traditionally thought of as regulators of single targets, display an array of central and peripheral actions, we found that OXT directly affects bone and body composition. The effect of OXT on bone remodeling is physiologically relevant, as elevated OXT levels during pregnancy and lactation cause calcium mobilization from the maternal skeleton for intergenerational calcium transfer towards fetal bone mineralization. There is an equally large body of evidence that has established the presence of OXT receptors (OXTRs) in the brain through which central functions, such as social bonding, and peripheral functions, such as the regulation of body composition, are exerted. To purposefully address effects of OXT on the brain, we used RNAscope to map OXT and OXTR expression, at the single transcript level, in the whole female and male mouse brains. Identification of brain nuclei with the highest OXT and OXTR transcript density sheds further light on functional OXT nodes that could be further interrogated experimentally to define new physiologic circuitry.