31 Neuroendocrinological aspects of social anxiety and aggression related disorders (Bedgood, Boggiano, & Turan, 2014; Mehta & Josephs, 2010; Mehta, Lawless DesJardins, van Vugt, & Josephs, 2017; Sapolsky, 1990, 1991; van Honk et al., 1999). Oxytocin Originally considered as having a key role in labor and lactation, in the past decade the neuropeptide oxytocin has gained more and more interest as a modulator of social cognition and behavior. Oxytocin has a very similar structure to vasopressin, and both neuropeptides are synthesized in the supraoptic and paraventricular nuclei of the hypothalamus (Johnson & Young, 2017). From there they are released, via the anterior pituitary, in the bloodstream. In addition, there are projections to the amygdala, lateral septum, nucleus accumbens, hippocampus, and ventral tegmental area (Ross & Young, 2009), which are areas involved in the fight–flight response. Oxytocin inhibits the output of the central amygdala to the PAG, whereas vasopressin excites this pathway (Huber, Veinante, & Stoop, 2005). There are indications that oxytocin attenuates the cortisol stress response (Cardoso, Kingdon, & Ellenbogen, 2014) and it is thought to have anxiolytic effects (Heinrichs & Domes, 2008). In addition, oxytocin enhances the salience of social information by increasing attention towards social cues and also increases the reward value of social stimuli (see for a review Crespi (2016)). During the control of social approach–avoidance behavior, oxytocin decreases amygdala responses during threat approach as a result of its anxiolytic properties (Radke et al., 2017, n = 57). Also, oxytocin administration promotes threat approach in low socially anxious men (Radke, Roelofs, & de Bruijn, 2013, n = 24, medium to large effect sizes). It has been proposed that oxytocin and testosterone have opposite effects on social cognition and behavior: where testosterone facilitates a dominance-related approach strategy which serves individual status defense, oxytocin promotes social exploration and in-group protection (Bos, Panksepp, et al., 2012; Reimers & Diekhof, 2015). It is important to note that the effects of oxytocin depend on social context and individual differences and can have both positive and negative social effects. Shamay-Tsoory & Abu-Akel, (2016) argue that oxytocin increases the salience of safety signals in a positive and supportive context, but on the other hand triggers orienting responses to threat and enhances anxiety in an unpredictable and threatening situation. It is likely that interactions between phasic dopaminergic signaling and oxytocin in the ventral tegmental area, nucleus accumbens, and amygdala modulate the effects of context and individual differences. Interactions of oxytocin and serotonin in the nucleus accumbens have been shown to be important in social interaction (Dölen, Darvishzadeh, Huang, & Malenka, 2013). 2
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