Oxytocin promotes functional coupling between paraventricular nucleus and both sympathetic and parasympathetic cardioregulatory nuclei

The neuropeptide oxytocin (OXT) facilitates prosocial behavior and selective sociality. In the context of stress, OXT also can down-regulate hypothalamic–pituitary–adrenal (HPA) axis activity, leading to consideration of OXT as a potential treatment for many socioaffective disorders. However, the mechanisms through which administration of exogenous OXT modulates social behavior in stressful environmental contexts are not fully understood. Here, we investigate the hypothesis that autonomic pathways are components of the mechanisms through which OXT aids the recruitment of social resources in stressful contexts that may elicit mobilized behavioral responses. Female prairie voles (Microtus ochrogaster) underwent a stressor (walking in shallow water) following pretreatment with intraperitoneal OXT (0.25 mg/kg) or OXT antagonist (OXT-A, 20 mg/kg), and were allowed to recover with or without their sibling cagemate. Administration of OXT resulted in elevated OXT concentrations in plasma, but did not dampen the HPA axis response to a stressor. However, OXT, but not OXT-A, pretreatment prevented the functional coupling, usually seen in the absence of OXT, between paraventricular nucleus (PVN) activity as measured by c-Fos immunoreactivity and HPA output (i.e. corticosterone release). Furthermore, OXT pretreatment resulted in functional coupling between PVN activity and brain regions regulating both sympathetic (i.e. rostral ventrolateral medulla) and parasympathetic (i.e. dorsal vagal complex and nucleus ambiguous) branches of the autonomic nervous system. These findings suggest that OXT increases central neural control of autonomic activity, rather than strictly dampening HPA axis activity, and provides a potential mechanism through which OXT may facilitate adaptive and context-dependent behavioral and physiological responses to stressors

Modulation of resting-state amygdala-frontal functional connectivity by oxytocin in generalized social anxiety disorder

Generalized social anxiety disorder (GSAD) is characterized by aberrant patterns of amygdala-frontal connectivity to social signals of threat and at rest. The neuropeptide oxytocin (OXT) modulates anxiety, stress, and social behaviors. Recent functional neuroimaging studies suggest that these effects are mediated through OXT’s effects on amygdala reactivity and/or amygdala-frontal connectivity. The aim of the current study was to examine OXT’s effects on amygdala-frontal resting-state functional connectivity (rsFC) in GSAD patients and healthy controls (HCs). In a randomized, double-blind, cross-over design, 18 GSAD and 18 HC participants received intranasal OXT (24 IU or 40.32 μg) or placebo (PBO) before resting-state functional magnetic resonance imaging. In individuals with GSAD, OXT enhanced rsFC of the left and right amygdala with rostral anterior cingulate cortex (ACC)/medial prefrontal cortex (mPFC), and in doing so, reversed (ie, ‘normalized’) the reduced amygdala-frontal connectivity observed relative to HCs evident on PBO. Higher social anxiety severity in GSAD subjects correlated with lower amygdala-ACC/mPFC connectivity on PBO and higher social anxiety also correlated with greater enhancement in amygdala-frontal connectivity induced by OXT. These findings show that OXT modulates a neural circuit known for social threat processing and emotion regulation, suggesting a neural mechanism by which OXT may have a role in the pathophysiology and treatment of social anxiety disorder