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Janet Amico, Conditional Oxytocin Receptor Knockout Mice: Targeting the Forebrain to Understand Behavior, Endocrinology, Volume 149, Issue 7, 1 July 2008, Pages 3254–3255, https://doi.org/10.1210/en.2008-0463
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Oxytocin (OT), a nine-amino acid peptide, is synthesized primarily in magnocellular neurons of the hypothalamic supraoptic and paraventricular nuclei, and transported to the posterior lobe of the pituitary gland for storage and release into the peripheral circulation. Peripherally released OT is essential for milk ejection during lactation and also facilitates contraction of the gravid uterus. OT that is synthesized in parvocellular neurons of the paraventricular nuclei and select forebrain areas is released within the central nervous system and believed to influence complex behaviors. OT is proposed to foster social interaction (1, 2), induce the onset of maternal behavior (3), lessen anxiety (4, 5) and aggression (6), and attenuate the neuroendocrine response to psychogenic stress (7–10).
OT produces its biological actions by attaching to and activating its receptor (11). The OT receptor (OTR) belongs to the family of G protein-coupled receptors, and contains seven transmembrane domains. Activation of the receptor by OT leads to stimulation of phospholipase C and activation of G α-q/11 (11). To date, a single gene has been identified that encodes the OTR. The OTR is expressed in reproductive-related tissues such as the mammary gland, uterus, ovary, and testis, as well as many nonreproductive-associated tissues such as the kidney, heart, osteoblast, thymus, vascular endothelium, and brain (11, 12). Species differences have been identified in the regional distribution and number of OTR binding sites in the brain. However, in most species the OTR is abundant in brain regions such as the amygdala, hippocampus, olfactory lobe, and hypothalamus (11, 12), which regulate many of the social, emotional, and neuroendocrine behaviors that OT is hypothesized to influence. The distribution and number of OTR binding sites in the brain have been reported to change during development. For example, OTRs that were identified in certain brain regions of infant rats were not identified in the same area of adult rats; the opposite has also been observed (11). Gonadal steroids regulate brain OTRs. Estrogen positively influences brain OTR expression, whereas progesterone has the opposite effect (11).
