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. Author manuscript; available in PMC: 2018 May 1.
Published in final edited form as: Neurosci Biobehav Rev. 2017 May;76(Pt A):87–98. doi: 10.1016/j.neubiorev.2017.01.034

Figure 1. Morphology, neuroanatomical projections, and release mechanisms of OT neurons.

Figure 1

This schematic represents current views of OT neuronal structure and function. Magnocellular and parvocellular OT neurons project to distinct targets. In addition to projections to the posterior pituitary, magnocellular OT axons can innervate extrahypothalamic forebrain and midbrain regions, and dendrites can contact the third ventricle. In contrast, parvocellular OT neurons are thought to project predominantly to hindbrain and brainstem regions. Glutamatergic networks link magnocellular OT neurons and are thought to synchronize pulsatile release into the periphery. Though not pictured, axon collaterals from some parvocellular OT neurons can synapse onto, excite, and trigger OT release from magnocellular OT neurons in the SON. OT is stored in LDCVs that populate the soma, dendrites, and axons but are typically absent in terminals; thus en passant release is thought to be the primary form of axonal OT release. Axonal and somatodendritic OT release can be triggered without depolarization via activation of MC4Rs or the activity of transmembrane proteins such as CD38. Following somatodendritic release, OT can bind to autoreceptors and prime OT neurons for firing, and may also volume diffuse to other central targets. Abbreviations: BBB=blood brain barrier; 3V=3rd ventricle.