Background: There is a documented association between affective disorders (e.g., depression and anxiety) and cardiovascular disease in humans. Chronic social stressors may play a mechanistic role in the development of behavioral and cardiac dysregulation. The current study investigated behavioral, cardiac, and autonomic responses to a chronic social stressor in prairie voles, a rodent species that displays social behaviors similar to humans.

Social experiences, both positive and negative, may influence cardiovascular regulation. Prairie voles (Microtus ochrogaster) are socially monogamous rodents that form social bonds similar to those seen in primates, and this species may provide a useful model for investigating neural and social regulation of cardiac function. Cardiac regulation has not been studied previously in the prairie vole. Radiotelemetry transmitters were implanted into adult female prairie voles under anesthesia, and electrocardiographic parameters were recorded. Autonomic blockade was performed using atenolol (8 mg/kg ip) and atropine methyl nitrate (4 mg/kg ip). Several variables were evaluated, including heart rate (HR), HR variability and the amplitude of respiratory sinus arrhythmia. Sympathetic blockade significantly reduced HR. Parasympathetic blockade significantly increased HR, and reduced HR variability and the amplitude of respiratory sinus arrhythmia. Combined autonomic blockade significantly increased HR, and reduced HR variability and respiratory sinus arrhythmia amplitude. The data indicate that autonomic function in prairie voles shares similarities with primates, with a predominant vagal influence on cardiac regulation. The current results provide a foundation for studying neural and social regulation of cardiac function during different behavioral states in this socially monogamous rodent model.

Posttraumatic stress disorder (PTSD) is associated with gastrointestinal and genitourinary comorbidities. These map onto the somatization disorder symptoms in the Diagnostic and Statistical Manual of Mental Disorders (APA, 1994) and the dissociative [conversion] disorders symptoms in the International Classification of Diseases taxonomy (WHO, 2007). Hyperemesis gravidarum (HG) is one of these symptoms and a gastrointestinal comorbidity of PTSD occurring in pregnancy. It is an idiopathic condition defined as severe vomiting with dehydration, metabolic imbalance, wasting, and hospital care-seeking. HG is more severe than the normative phenomenon of nausea and vomiting of pregnancy (NV). This test-of-concept pilot (N=25) explored the hypothesis that there is a trauma-related subtype of HG characterized by (1) high levels of dissociative symptoms and (2) altered plasma concentrations of oxytocin. This hypothesis is informed by a theory of posttraumatic oxytocin dysregulation positing altered oxytocin function as a mechanism of gut smooth muscle peristalsis dysfunction. A four-group analysis compared controls with nausea and vomiting of pregnancy (NV only) and cases with HG only, NV and PTSD, or HG and PTSD. Oxytocin was correlated with nausea and vomiting symptom severity score (r = .464, p = .019) and with the dissociation symptom score (r = .570, p = .003). Women in the group with both PTSD and HG (the “trauma-related HG subtype”) had the highest levels of dissociation and the highest levels of oxytocin. A linear regression model indicated that the independent association of the trauma-related HG subtype with oxytocin level was mediated by high levels of dissociative symptoms.

Although heart rate and temperature are continuously monitored in patients during recovery following surgery, measures that extract direct manifestations of neural regulation of autonomic circuits from the beat-to-beat heart rate may be more sensitive to outcome. We explore the relationship between features of autonomic regulation and survival in the prairie vole, a small mammal, with features of vagal regulation of the heart similar to humans. Cardiac vagal regulation is manifested in the beat-to-beat heart rate variability (HRV) pattern and can be quantified by extracting measures of the amplitude of periodic oscillations associated with spontaneous breathing. Thus, monitoring beat-to-beat heart rate patterns post-surgery in the prairie vole may provide an opportunity to dynamically assess autonomic adjustments during recovery. Surgeries to implant telemetry devices to monitor body temperature and continuous ECG in prairie voles are routinely performed in our laboratory. Ten of these implanted prairie voles died within 48 h post-surgery. To compare the post-surgery autonomic trajectories with typical surviving prairie voles, the post-surgery data from 17 surviving prairie voles were randomly selected. The data are reported hourly for 27 prairie voles between 6 and 14 h (1 h before the demise of the first subject) post-surgery. Receiver operator curves were calculated hourly for each variable to evaluate sensitivity in discriminating survival. The data illustrate that measures of HRV are the most sensitive indicators. These findings provide a foundation for investigating further neural mechanisms of cardiovascular function.