Abstract
Oxytocin (OT) is a neuropeptide produced by hypothalamic neurons and is known to modulate social behavior among other functions. Several experiments have shown that OT modulates neuronal activity in many brain areas, including sensory cortices. OT neurons thus project axons to various cortical and subcortical structures and activate neuronal subpopulations to increase the signal-to-noise ratio, and in turn, increases the saliency of social stimuli. Less is known about the origin of inputs to OT neurons, but recent studies show that cells projecting to OT neurons are often located in regions where the OT receptor (OTR) is expressed. Thus, we propose the existence of reciprocal connectivity between OT neurons and extrahypothalamic OTR neurons to tune OT neuron activity depending on the behavioral context. Furthermore, the latest studies have shown that OTR-expressing neurons located in social brain regions also project to other social brain regions containing OTR-expressing neurons. We hypothesize that OTR-expressing neurons across the brain constitute a common network coordinated by OT.
Highlights
Oxytocin (OT) is a neuropeptide mainly synthesized in the paraventricular (PVN), supraoptic (SON), and accessory nuclei of mammalian hypothalamus and is present, with some minor molecular variations, in all vertebrates (Knobloch and Grinevich, 2014; Banerjee et al, 2016)
The current leading hypothesis to explain OT effects on social behavior is that the neuropeptide selectively increases the saliency of socially relevant stimuli in areas enriched with OT receptor (OTR)-expressing neurons (Shamay-Tsoory and Abu-Akel, 2015; Marlin and Froemke, 2016)
The authors showed that optogenetically evoked release of OT from axons residing in the anterior olfactory nucleus (AON) stimulates olfactory exploration and social recognition, while ablation of OTR in this cortex resulted in a ‘‘social amnesia’’ (Oettl et al, 2016)
Summary
Oxytocin (OT) is a neuropeptide mainly synthesized in the paraventricular (PVN), supraoptic (SON), and accessory nuclei of mammalian hypothalamus and is present, with some minor molecular variations, in all vertebrates (Knobloch and Grinevich, 2014; Banerjee et al, 2016) This peptide has two general ways of action: first, via projections to the posterior pituitary, it is secreted into the bloodstream as a hormone controlling various physiological processes, such as parturition, lactation, energetic metabolism, cardiovascular function, bone homeostasis, and muscle maintenance (Neumann et al, 1993; Gutkowska and Jankowski, 2012; Chaves et al, 2013; Kasahara et al, 2013; Elabd et al, 2014; Poisbeau et al, 2017; Sun et al, 2019). OT acts in the brain as a non-canonical neurotransmitter or neuromodulator, regulating a number of behaviors ranging from pain to social behaviors (Macdonald and Feifel, 2014; Bowen and Neumann, 2017; Grinevich and Stoop, 2018; Lawson et al, 2019)
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