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. 2017 Jul 4;38(1):209–217. doi: 10.1007/s10571-017-0517-x

Posttraumatic Stress Disorder Disturbs Coronary Tone and Its Regulatory Mechanisms

Svetlana S Lazuko 1, Olga P Kuzhel 1, Lyudmila E Belyaeva 1, Eugenia B Manukhina 3,2,4, H Fred Downey 4, Olga B Tseilikman 2, Maria V Komelkova 2, Vadim E Tseilikman 2,✉
PMCID: PMC11481920  PMID: 28676988

Abstract

Posttraumatic stress disorder (PTSD) is associated with myocardial injury, but changes in coronary regulatory mechanisms in PTSD have not been investigated. This study evaluated the effect of PTSD-inducing stress on coronary tone and its regulation by nitric oxide (NO) and voltage-gated K+ channels. PTSD was induced by exposing rats to predator stress, 15 min daily for 10 days, followed by 14 stress-free days. Presence of PTSD was confirmed by the elevated plus-maze test. Coronary tone was evaluated from changes in coronary perfusion pressure of Langendorff isolated hearts. Predator stress induced significant decreases in coronary tone of isolated hearts and in blood pressure of intact rats. L-NAME, a non-selective NO synthase (NOS) inhibitor, but not S-MT, a selective iNOS inhibitor, and increased coronary tone of control rats. In PTSD rats, both L-NAME and S-MT increased coronary tone. Therefore, the stress-induced coronary vasodilation resulted from NO overproduction by both iNOS and eNOS. NOS induction was apparently due to systemic inflammation as evidenced by increased serum interleukin-1β and C-reactive protein in PTSD rats. Decreased corticosterone in PTSD rats may have contributed to inflammation and its effect on coronary tone. PTSD was also associated with voltage-gated K+ channel dysfunction, which would have also reduced coronary tone.

Keywords: Posttraumatic stress disorder, Coronary tone, NO synthase, Corticosterone, Interleukin-1β, C-reactive protein

Introduction

Posttraumatic stress disorder (PTSD) is a delayed response to stressful events or to a threatening or catastrophic situation (Pitman et al. 2012). Delayed effects of severe psychological trauma are evident as various psychosomatic conditions, including cardiovascular diseases (Koenen et al. 2017). In laboratory animals, cardiovascular disorders characteristic of PTSD, including myocardial ischemic injury, were produced using a predator-exposure model based on natural rodent fear of a predator (close proximity of a cat or exposure to cat urine) (Zoladz and Diamond 2016). Although there are multiple reports of PTSD-associated myocardial ischemic disorders (Bryan et al. 2009), the role of altered coronary vascular tone in these conditions has not been studied.

Nitric oxide (NO) is a well-known regulator of vascular tone (Bryan et al. 2009). NO is synthesized from l-arginine by three NO synthase (NOS) isoforms, neuronal (nNOS), inducible (iNOS), and endothelial (eNOS). nNOS occurs primarily in neurons, but small amounts are also found in cardiac and vascular cells (Vincent and Hope 1992; Maccallini and Amoroso 2016; Costa et al. 2016). eNOS is expressed in the vascular endothelium. Both nNOS and eNOS activities are Ca2+-dependent (Godo and Shimokawa 2016). iNOS is expressed mostly in activated macrophages in response to proinflammatory cytokines, and its activity is Ca2+-independent. iNOS generates three orders of magnitude more NO than eNOS or nNOS and, therefore, is mainly responsible for NO overproduction in conditions associated with stress and inflammation (Nathan 1995).

Another important mechanism of vascular tone regulation is activation of voltage-gated K+ channels (Kv) in vascular smooth muscle (Palen et al. 2005). Kv channel activation causes membrane hyperpolarization, reduced Ca2+ influx through voltage-gated Ca2+ channels, and decreased smooth muscle contractions (Jaggar et al. 1998). Thus, dysfunction of Кv channels can lead to vasoconstriction or impaired arterial vasodilation (Nelson and Quayle 1995).

In stress, vascular tone and blood pressure are extensively influenced by glucocorticoids, which are key stress hormones (Sapolsky et al. 2000). Effects of glucocorticoids on the cardiovascular system can be direct and also mediated by modulation of inflammatory processes and NOS activity (Goodwin 2015). In this study, we focused on changes in coronary vascular tone in PTSD and evaluated possible mechanisms of post-stress disorders in coronary tone regulation.

Materials and Methods

Experimental Animals

Experiments were performed on 86 white mongrel male rats, weighing 180–240 g. Rats were housed in standard rat cages and provided rat chow and tap water ad libitum. The temperature in the housing facility was controlled at 21 °C, and lights were set to a 12:12-h light–dark cycle. All animal experiments conformed to requirements of the Council for International Organizations of Medical Sciences (CIOMS) and the International Council for Laboratory Animal Science (ICLAS) as described in “International Guiding Principles for Biomedical Research Involving Animals.” The study protocol was approved by the Committee for Bioethics and Humane Treatment of Laboratory Animals at Vitebsk State Medical University.

Experimental Protocol

The protocol for modeling PTSD, evaluating the stress-related rat behavior, measuring blood pressure (BP), blood collection for biochemical tests, and experiments on isolated heart were according to the following schedule:

Days 1–5: further adaptation to experimental conditions; daily BP measurements.

Days 6–16: predator scent stress.

Days 17–30: rest and prospective development of experimental PTSD.

Days 30–34: rest and prospective development of experimental PTSD; daily BP measurements.

Day 35: plus-maze test.

Day 36: sacrificing rats with blood collection or excision of heart for isolated heart experiments.

Handling of unstressed, control rats, and stressed rats was identical.

Modeling PTSD

To induce PTSD, rats were exposed to cat urine scent for 15 min daily for 10 days (days 6–16 of the protocol). Following this stress, the rats experienced normal conditions for 14 days before BP was measured and behavioral tests were performed.

This PTSD model is based on the model described by Cohen & Zohar (Cohen and Zohar 2004), which involves a single exposure of rats to cat urine. This model was modified by increasing the number of daily predator scent exposure from one to ten, taking into account the fact that PTSD is often observed in veterans of wars, who are subjected to repeated stress (Rutkowski and Dembinska 2016). Predator stress, which is a stress of enemy presence, is considered a model of military stress (Daskalakis and Yehuda 2014). Our model was characterized in detail by Kondashevskaya et al. (2017). This model was used also in an earlier, related study (Kolesnikova et al. 2015).

Measuring Blood Pressure

BP was measured by the tail cuff method daily on days 1–5 and 30–34 of the protocol. BP values for these respective intervals were averaged. The plus-maze test was done on the day following the last BP measurement.

Elevated X-Maze Test

The predator stress outcome was evaluated using the elevated plus-maze test (Lapiz-Bluhm et al. 2008; Serova et al. 2013). Recorded variables included the time spent in open and closed arms of the maze and the number of entries into the open and closed arms. The behavior of rats in the maze was recorded and tracked using the video system SMART and analyzed with SMART 3.0 software. Based on these measurements, an anxiety index (AI) was calculated (Cohen et al. 2008):

AI=1-time in open arms/∑time on maze+number of entries into open arms/∑number of entries/2

Blood Collection and Storage

Between 11.00 am and 1.00 pm on day 36 of the protocol, rats were sacrificed by decapitation under ether anesthesia, and blood was collected. Blood serum was removed from clotted blood and stored frozen in Eppendorf tubes at –20 °C. After unfreezing, serum concentrations of corticosterone, interleukin-1β, C-reactive protein, and iNOS were measured.

Experiments on Langendorff Isolated Heart

On day 36 of the protocol, rats were anesthetized with urethane, and their hearts were rapidly excised for isolated heart experiments as described earlier (Lazuko et al. 2016).

Coronary Perfusion Pressure

Coronary vascular tone was evaluated by monitoring coronary perfusion pressure (CPP) measured in Langendorff isolated hearts using a IH-SR 844/1 system (HSE-HA, Germany) equipped with Isotec pressure transducers for measuring aortic and developed intraventricular pressures. Isolated hearts were perfused at a constant coronary flow of 10 ml/min with Krebs–Henseleit buffer solution aerated with 95% O2 + 5% CO2. Computer recording and processing of the measured variables were performed with software ACAD (HSE, Germany). Each experiment included perfusion of the heart without or with an inhibitor of mechanisms that regulate coronary tone.

The hearts were electrically paced at 240 beats/min (pulse width, 5.0 ms; amplitude, 20 V). CPP was first measured after a 15-min stabilization period. CPP was recorded for 5 min, the perfusion buffer was replaced with a similar buffer containing one of the study inhibitors (L-NAME, S-MT, or 4-AP), and CPP was recorded for another 5 min. All agents were added to the perfusion buffer. S-MT and L-NAME were diluted directly in Krebs–Henseleit buffer solution and 4-AP was dissolved in distilled water and then added to the perfusion solution. The total duration of an experiment was 25 min.

Evaluation of iNOS and eNOS Contributions to Coronary Tone Regulation

To study the role of NO produced by iNOS and eNOS in the regulation of coronary tone, a selective iNOS inhibitor, S-methylisothiourea (S-MT, 10−6 M, Sigma-Aldrich, Inc., St. Louis, MO, USA) and a non-selective NOS inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME, 60 µM, Sigma-Aldrich, Inc., St. Louis, MO, USA) were used. The effects of these inhibitors were assessed from changes in coronary perfusion pressure. The role of NO produced by eNOS was estimated from the difference between the effects of L-NAME and S-MT.

Evaluation of Kv Channel Contribution to Coronary Tone Regulation

To study the role of Kv channels in regulation of coronary tone, a Kv channel blocker, 4-aminopyridine (4-AP, 1.5 mM Sigma-Aldrich, Inc., St. Louis, MO, USA) was used. The Kv channel contribution was determined by the magnitude of coronary response to 4-AP, i.e., the increment in coronary perfusion pressure.

Measurement of Serum Corticosterone

Corticosterone concentration was measured by ELISA using test kits (Bioclin, Cardiff, UK) according to the manufacturer’s instruction. The assay sensitivity was 0.25 ng/ml, and the intra- and inter-assay coefficients of variation were both <5%.

Measurement of Serum Interleukin-1β

IL-1β concentrations were measured by ELISA using test kits (Thermo Scientific, USA, Lot LD145322) and expressed as pg/ml. The assay sensitivity was ≤1 pg/mL and the intra- and inter-assay coefficients of variation were both <10%.

Measurement of Serum C-Reactive Protein

C-reactive protein concentrations were measured by ELISA using test kits (Vektor-Best, Russia). The sensitivity of the assay was 0.05 mg/l, and the intra- and inter-assay coefficients of variation were both <5%.

Measurement of Serum iNOS

iNOS concentrations were measured by ELISA using test kits (USCN, Life Science Inc. China, Lot L130827587) and expressed as ng/ml. Photometry was performed at λ = 450 nm. The assay sensitivity was defined as the lowest protein concentration that could be differentiated from zero. Detection range, 1.56–100 nmol/l).

Statistical Analysis

Data were analyzed statistically with STATISTICA 10.0 and MS Excel software. Quantitative data are presented as mean ± SEM. Due to absence of normal distributions of the data, as shown by the Shapiro–Wilks test for normality, the non-parametric Mann–Whitney U test was used to determine significance of differences between independent groups. Statistical hypotheses were tested at the critical significance level of 5% (p < 0.05).

Results

Behavioral Testing in Elevated X-Maze

The anxiety index was significantly increased in rats with PTSD compared to control animals (control, 0.61 ± 0.05; PTSD, 0.88 ± 0.07, p < 0.05). The post-stress increase in anxiety index was due to (1) a shorter stay in open arms of the elevated x-maze (control, 67.3 ± 5.4 s; PTSD, 39.8 ± 5.3 s; p < 0.05); (2) a decreased ratio of time spent in open arms to the total test time (control, 0.14 ± 0.05; PTSD, 0.05 ± 0.01; p < 0.05); (3) the number of entries into open arms (control, 4.2 ± 0.2; PTSD, 2.5 ± 0.07; p < 0.05); (4) the decreased ratio of the number of entries to open arms to the total number of entries (control, 0.54. ± 0.01; PTSD, 0.27 ± 0.009; p < 0.05). There were no statistically significant changes in (1) the time of stay in closed arms; (2) the number of entries into closed arms; (3) the ratio of time spent in closed arms to the total test time; (4) the ratio of the number of entries to closed arms to the total number of entries. Overall, these results indicated increased anxiety in rats exposed to predator stress.

Effect of Predator Stress on Systemic Blood Pressure

Table 1 shows BP and heart rate data. During protocol days 1–5, control systolic BP (SBP) was 119 ± 2.7 mm Hg, diastolic BP (DBP) was 88 ± 4.2 mm Hg, mean BP was 101 ± 2.6 mm Hg, and heart rate was 303 ± 6.1 bpm. Rats assigned to the PTSD group had similar pre-stress values for BP and heart rate. By protocol days 30–34, these values had not changed significantly in unstressed, control rats. In stressed rats of the PTSD group, by protocol days 30–34, SBP had decreased 20%, DBP had decreased 23%, mean BP had decreased 21%, and the heart rate had increased 15%. These systemic hemodynamic changes were all statistically significant (p < 0.05) when compared to pre-stress values and when compared to respective values measured in unstressed, control rats. These results indicated that exposure to predator stress significantly affected systemic hemodynamics by lowering BP and by increasing heart rate.

Table 1.

PTSD-associated changes in blood pressure and heart rate

Groups Systolic BP (mm Hg) Diastolic BP (mm Hg) Mean BP (mm Hg) Heart rate, beats/min
Control, pre-stress measurement on Days 1–5 (n = 11) 119 ± 2.7 88 ± 4.2 101 ± 2.6 303 ± 6.1
Control, post-stress measurement on Days 30–34 (n = 11) 121 ± 2.1 84 ± 3.3 100 ± 2.1 310 ± 7.4
PTSD, pre-stress measurement on Days 1–5 (n = 10) 120 ± 4.1 81 ± 2.7 99 ± 1.1 307 ± 3.2
PTSD, post-stress measurement on Days 30–34 (n = 10) 95 ± 2.9*,# 68.9 ± 3.3*,# 80.2 ± 1.8*,# 356 ± 6.1*,#
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* Significant difference from control, p < 0.05

# Significant difference from the PTSD pre-stress measurement, p < 0.05, n = number of rats per group

Effect of Predator Stress on Coronary Perfusion Pressure

Coronary perfusion pressure (CPP) was 81 ± 2.5 mm Hg in the control group; in the PTSD group, CPP was decreased to 56.5 ± 4.9 (30%) compared to the control (p < 0.05). This result reflects changes in coronary vascular tone and shows that exposure to predator stress significantly decreased it.

Effects of NOS Inhibitors on Coronary Perfusion Pressure

In hearts from control animals, the non-selective NOS inhibitor, L-NAME (control + L-NAME group) induced a significant increase in coronary tone (Fig. 1); CPP increased from 81 ± 2.5 to 127 ± 7.8 mm Hg (56%, p < 0.05). In contrast, the selective iNOS inhibitor, S-MT induced no changes in CPP. Therefore, under physiological conditions, iNOS did not significantly regulate coronary tone.

Fig. 1.

Fig. 1

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Effect of the non-selective NOS inhibitor, L-NAME, and the selective iNOS inhibitor, S-MT, on PTSD-associated changes in coronary perfusion pressure (CPP) of isolated hearts perfused at constant flow. *Significantly different from control, p < 0.05. #Significantly different from PTSD, p < 0.05

In the presence of PTSD-reduced CPP, L-NAME induced a significant increase in CPP (Fig. 1); 39% greater CPP in the PTSD + L-NAME group compared with the PTSD group. CPP increased by 39% to 92 ± 5.5 mm Hg, which was comparable to the CPP of the control group. In PTSD rats, as distinct from control rats, the selective iNOS inhibitor, S-MT, induced a significant increase in CPP (Fig. 1).

Effects of Kv Channel Inhibitor on Coronary Perfusion Pressure

In isolated hearts of control rats, CPP was 81 ± 2.5 mm Hg. Figure 2 shows that the Kv channel inhibitor, 4-AP, increased CPP to 139.8 ± 4.2 mm Hg (72%, p < 0.05). In the hearts of PTSD rats, 4-AP increased CPP to 70.8 ± 6.3 mm Hg (23%, p < 0.05 vs. control + 4-AP) (Fig. 2). Therefore, this decreased effect of 4-AP demonstrated that Kv channels were dysfunctional in PTSD.

Fig. 2.

Fig. 2

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Effect of the Kv channel selective inhibitor, 4-AP, on PTSD-associated changes in coronary perfusion pressure (CPP) of isolated hearts perfused at constant flow. *Significantly different from control, p < 0.05. #Significantly different from PTSD, p < 0.05

Effect of Predator Stress on Serum Concentrations of Corticosterone, Interleukin-1β, C-Reactive Protein, and iNOS

In PTSD rats, serum concentration of corticosterone was significantly lower than in control rats (420.73 ± 116.9 nmol/L in control vs. 192.81 ± 101.14 nmol/L in PTSD, p < 0.005). Serum concentration of IL-1β was more than 30 times higher in PTSD rats than in control rats (20.3 ± 4.1 pg/ml in PTSD vs. 0.6 ± 0.1 pg/ml in control, p < 0.029). Serum concentration of C-reactive protein was 28% higher in PTSD rats than in control rats (0.49 ± 0.02 mg/l in PTSD vs. 0.38 ± 0.01 mg/l in control, p < 0.004). Serum concentration of iNOS was significantly higher in PTSD rats than in control rats (112.9 ± 16.5 ng/ml in PTSD vs. 2.7 ± 0.2 in control, p < 0.05).

Discussion

In this study, a PTSD-associated decrease in CPP, reflecting a respective decrease in vascular tone, was observed for the first time. This decrease in CPP involved an NO-dependent mechanism, since L-NAME, a non-selective NOS inhibitor, blunted the stress-induced decrease in CPP. S-MT, a selective iNOS inhibitor, also blunted the stress-induced decrease in CPP, demonstrating a contribution of iNOS to this effect of predator stress on coronary tone. In physiological conditions, S-MT did not induce any pressor response; therefore, iNOS played a role in the changes of CPP only in PTSD. L-NAME increased CPP in isolated hearts from both control and PTSD rats. Since this non-selective NOS inhibitor more completely blunted the stress-induced decrease in CPP than the selective iNOS inhibitor, S-MT, NOS isoforms other than iNOS must also contribute to stress-induced dilation of coronary vessels. These findings are consistent with the notion that PTSD is associated with both increased expression of iNOS in macrophages and myocardium and of eNOS in the coronary endothelium.

Voltage-gated K+ channels (Кv) play an important role in the regulation of coronary vascular tone. Normally, activation of Кv channels in smooth muscle cells is associated with closure of voltage-gated Ca2+ channels, decreased Ca2+ influx, and smooth muscle relaxation (Cole et al. 1996); therefore, inhibition of Kv channels induces vasoconstriction. In this study, the Kv channel blocker, 4-AP, exerted pronounced vasoconstriction in control rats, which was not observed in PTSD rats. This result demonstrated that stress causes Кv channel dysfunction. In this study, predator stress induced a decrease in CPP, which did not respond to 4-AP. Therefore, this stress-induced decrease in CPP was not due to activation of Kv channels. It is possible that PTSD-induced Кv channel dysfunction might counterbalance to some extent the NOS activation caused by predator stress.

The current investigation examined coronary vascular control mechanisms two weeks after exposure to stress and found reduced CPP suggesting reduced coronary tone. In contract, myocardial ischemic injury has been reported at 30 or more days following exposure to traumatic stress (Zoladz and Diamond 2016). The possibility that myocardial ischemia results when stress-induced Кv channel dysfunction persists after NOS activation wanes merits investigation.

In this study, experimental PTSD was associated not only with reduced coronary vascular tone but also with reduced systemic BP. This seems inconsistent with the findings of some studies that predator stress or chronic stress induces hypertension. Those studies employed either a single exposure to predator stress (Zoladz et al. 2013) or chronic exposures to relatively mild stressors, such as hypokinesia or social isolation (Cruz et al. 2016). In many experiments where stress-induced hypertension was observed, special rat strains prone to hypertension were used (Mansi and Drolet 1997; McDougall et al. 2000; Cui et al. 2003) or additional treatments (salt, chronic hypoxia, etc.) were employed which facilitated an increase in BP (Porter and King 2009; Ma et al. 2008). Otherwise, acute or chronic restraint stress may not induce significant hypertension (Filaretova et al. 2013; Carda et al. 2015). The model we used involved multiple exposures to predator scent; therefore, the stress was prolonged and severe. According to the Selye concept, responses to such severe stress can progress from the resistance phase, characterized by hypertension, to the exhaustion phase, characterized by hypotension (Selye 1950). In fact, reduced vascular tone and systemic hypotension are typical models of severe stress (Yip and Krukoff 2002; Yoshino et al., 2005; Solodkov et al. 2014; Meerson and Manukhina 1985). Our data are also consistent with the results of a clinical study where veterans with PTSD had orthostatic hypotension (Oddone et al. 2015). Other studies showed that Gulf War veterans with PTSD were more prone to orthostatic systolic hypotension than control subjects (Peckerman et al. 2003), and that Gulf War veterans with chronic fatigue syndrome had neurally mediated hypotension (Davis et al. 2000). Earlier studies suggested that overproduction of nitric oxide may account for post-stress hypotension (Yip and Krukoff, 2002; Manukhina et al. 2011).

Reduced corticosterone levels were found in both PTSD rats (Cohen et al. 2006) and in patients with PTSD (Yehuda 1997). Hypocorticosteronemia is considered an important phenomenological and biological correlate of PTSD (Oosthuizen et al. 2005) and a marker of vulnerability to chronic PTSD (Yehuda 2000). Apparently, the reduced corticosterone level, along with other regulatory disorders, such as impaired sympathetic vasoconstriction (Rose et al. 2006; Shah et al. 2013), contributed to hypotension in PTSD (Malerba et al. 2005).

One of the glucocorticoid antihypotensive mechanisms is mediated by downregulation of NOS expression and, thus, reduced production of NO, a potent vasodilator. Glucocorticoids prevent excessive activation of iNOS and eNOS in inflammation via endothelial glucocorticoid receptors (Szabo et al. 1994). However, in PTSD, there is persistently increased iNOS production, resulting in excessive, toxic amounts of NO (for review see Oosthuizen et al. 2005). PTSD is associated with immediate activation of NOS, specifically iNOS (Harvey et al. 2004), which may last as long as three weeks (Oosthuizen et al. 2005). PTSD is associated with increased 2001secretion of proinflammatory cytokines, including IL-6 and IL-1β (Maes et al. 1999; Baker et al. 2001; Passos et al. 2015). Normally, glucocorticoids suppress cytokine secretion (Sapolsky et al. 2000; Baker et al. 2001); however, in PTSD, the reduced glucocorticoid levels promote systemic inflammation. In this study, experimental PTSD was associated with increased concentrations of both IL-1β and C-reactive protein, a marker of systemic inflammation. These results are consistent with clinical data showing that C-reactive protein was positively correlated with PTSD severity in the survivors of the 9/11 terroristic attack (Rosen et al. 2017). Other clinical studies have also demonstrated development of systemic inflammation in PTSD (Haroon et al. 2012).

In the process of systemic inflammation, cytokines induce iNOS expression (Mangge et al. 2014). In PTSD, increased iNOS expression was found in brain (Harvey et al. 2004), and in this study increased iNOS concentration was found in serum for the first time. Apparently, the increased iNOS expression in PTSD occurs at the systemic level. Thus, stress-induced activation of NOS and production of large amounts of NO reduce vascular tone not only in the coronary circulation, but apparently also in the systemic circulation, and, thus, are an important factor in the systemic hypotension of PTSD.

Conclusion

Results of this study demonstrated for the first time that experimental PTSD was associated with reduced CPP, reflecting reduced coronary vascular tone. Systemic hypotension was also evident. The decrease in CPP was associated with the activation of iNOS, which can produce large amounts of NO, a potent vasodilator. eNOS also contributed to this effect. iNOS expression was most likely induced by systemic inflammation, as indicated by increased interleukin-1β and C-reactive protein. Reduced serum corticosterone in PTSD contributes to both systemic inflammation and hypotension. At the same time, PTSD was associated with depressed functional activity of Kv channels, which would restrict coronary vasodilation. Further studies are required to more completely delineate mechanisms of the post-stress decline in BP and to evaluate a possible role of Kv channel dysfunction in the development of myocardial ischemic injury of prolonged PTSD. Results of this study may be useful in developing new methods for prevention and treatment of cardiovascular disorders in patients with PTSD.

Acknowledgements

The South Ural State University is grateful for financial support of the Ministry of Education and Science of the Russian Federation (Grant #17.7255.2017/8.9) and the Russian Science Foundation (Grant #17-15-013418). This work was supported by Act 211 Government of the Russian Federation, contract #02.A03.21.0011.

Statement of Author Contribution

All authors participated in the design, interpretation of the studies, analysis of the data, and review of the manuscript; SSL isolated heart and measured BP; OPK performed PTSD model and measured coronary pressure, LEB measured concentrations of C-reactive protein, IL-1β, and iNOS; EBM and HFD expanded and edited the manuscript and assisted with data interpretation; OBT performed elevated plus-maze test; MVK measured concentration of corticosterone; VET designed the study and drafted the manuscript.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical Approval

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.

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