Sex-Based Contributors to and Consequences of Post-traumatic Stress Disorder

Activation of trace amine-associated receptor 1 ameliorates PTSD-like symptoms

Trace amine-associated receptor 1 (TAAR1) negatively modulates monoaminergic transmission in the mammalian brain and participates in many psychiatric disorders. Preclinical evidence indicate that selective TAAR1 agonists have anxiolytic effects and anti-stress properties. Post-traumatic stress disorder (PTSD) is an anxiety disorder triggered by experiencing or witnessing traumatic stressors. However, it remains unknown whether TAAR1 is involved in PTSD. Here, we investigated the role of TAAR1 in two PTSD animal models, including single prolonged stress (SPS)-induced impairment of fear extinction and stress-enhanced fear learning (SEFL). SPS decreased TAAR1 mRNA levels in the prefrontal cortex and ventral tegmental area. Acute treatment of the TAAR1 partial agonist RO5263397 attenuated SPS-induced anxiety-like behavior evaluated by the elevated-plus maze test. Compared to non-stressed animals, rats that experienced SPS showed higher freezing levels in the extinction retention test, indicating an impairment of fear extinction retention after SPS exposure. Acute and chronic treatment of RO5263397 ameliorated SPS-induced impairment of fear extinction retention. In the SEFL model, compared to the No-shock group, rats that experienced severe foot shock before fear conditioning showed higher freezing levels during the tests, indicating enhanced fear learning after stress exposure. Chronic treatment of RO5263397 partially attenuated the SEFL. Moreover, chronic treatment with the selective TAAR1 full agonist RO5166017 completely prevented the SEFL. Taken together, these data showed that pharmacological activation of TAAR1 could ameliorate PTSD-like symptoms. The present study thus provides the first evidence that TAAR1 might participate in the development of PTSD, and TAAR1 agonists could be potential pharmacological treatments for this disorder.

Sex-dependent effects of angiotensin type 2 receptor expressing medial prefrontal cortex (mPFC) interneurons in fear extinction learning

Background

The renin-angiotensin system (RAS) has been identified as a potential therapeutic target for PTSD, though its mechanisms are not well understood. Brain angiotensin type 2 receptors (AT2Rs) are a subtype of angiotensin II receptors located in stress and anxiety-related regions, including the medial prefrontal cortex (mPFC), but their function and mechanism in the mPFC remain unexplored. We therefore used a combination of imaging, cre/lox, and behavioral methods to investigate mPFC-AT2R-expressing neuron involvement in fear learning.

Methods

To characterize mPFC-AT2R-expressing neurons in the mPFC, AT2R-Cre/td-Tomato male and female mice were used for immunohistochemistry (IHC). mPFC brain sections were stained with glutamatergic or interneuron markers, and density of AT2R+ cells and colocalization with each marker was quantified. To assess fear-related behaviors in AT2R-flox mice, we selectively deleted AT2R from mPFC neurons using an AAV-Cre virus. Mice then underwent Pavlovian auditory fear conditioning, approach/avoidance, and locomotion testing.

Results

IHC results revealed that AT2R is densely expressed in the mPFC. Furthermore, AT2R is primarily expressed in somatostatin interneurons in females but not males. Following fear conditioning, mPFC-AT2R deletion impaired extinction in female but not male mice. Locomotion was unaltered by mPFC-AT2R deletion in males or females, while AT2R-deleted females had increased exploratory behavior.

Conclusion

These results lend support for mPFC-AT2R+ neurons as a novel subgroup of somatostatin interneurons that influence fear extinction in a sex-dependent manner. This furthers underscores the role of mPFC in top-down regulation and a unique role for peptidergic (ie., angiotensin) mPFC regulation of fear and sex differences.

Patient journey before and after a formal post-traumatic stress disorder diagnosis in adults in the United States - a retrospective claims study

OBJECTIVE

To describe post-traumatic stress disorder (PTSD)-related symptoms and frequent psychiatric comorbidities, treatments received, healthcare resource utilization (HRU), and healthcare costs pre- and post-PTSD diagnosis among adults in the United States.

METHODS

Adults with PTSD who received a PTSD-related pharmacological treatment (selective serotonin reuptake inhibitor [SSRI], serotonin-norepinephrine reuptake inhibitor [SNRI], atypical antipsychotic [AA]) within 24 months of the first observed PTSD diagnosis (index date) were identified using MarketScan Commercial Database (2015-2020). Study outcomes were assessed during the 6-month pre-diagnosis and 24-month post-diagnosis periods. Subgroup analyses included patients treated or not treated with AAs post-PTSD diagnosis.

RESULTS

Of the overall patients (N = 26,306; mean age at diagnosis 39.5 years; 73.3% female), 85.9% had PTSD-related symptoms and frequent psychiatric comorbidities during the 6 months pre-diagnosis. Patients treated with AAs post-PTSD diagnosis (N = 9,298) tended to have higher rates of PTSD-related symptoms and comorbidities at diagnosis than those not treated with AAs (N = 7,011). Following diagnosis, the most commonly observed first-line treatments were SSRI (67.4%), AA (23.4%), and SNRI (22.6%). The rate of PTSD-related symptoms and comorbidities, psychotherapy and pharmacological treatments received, HRU, and healthcare costs increased during the 6 months post-diagnosis relative to the 6 months pre-diagnosis and then declined over time during the 24 months post-diagnosis.

CONCLUSIONS

The PTSD diagnosis was associated with increased rates of symptoms and frequent psychiatric comorbidities, psychotherapy and pharmacological treatments received, HRU, and healthcare costs, pointing to increased patient monitoring. Within 6 to 12 months after the PTSD diagnosis, these outcomes tended to reduce, perhaps as patients were obtaining targeted and effective care.