In the brain, OXT is not only released from the posterior pituitary, but these magnocellular neurons of the SON and PVN also possess axon collaterals that extend long range projections to various forebrain regions, including the prefrontal cortex (PFC), anterior olfactory nucleus, nucleus accumbens (NAc), lateral septum (LS), hippocampus (HIPP), bed nucleus of the stria terminalis (BNST) and amygdala (Stoop, 2012). Oxytocin synthesis also occurs in smaller parvocellular neurons of the PVN and, to a lesser degree, in selective extra-hypothalamic neurons (Jurek and Neumann, 2018). These neurons are distinct from magnocellular populations in that they do not release OXT into the bloodstream (Knobloch and Grinevich, 2014). Parvocellular OXT neurons project mainly to the brainstem and spinal cord where they synapse to effect autonomic functions, pain regulation and analgesia (Eliava et al., 2016).
