The establishment of rat model in myocardial ischemia with psychological stress

Psychological stress can provoke and aggravate myocardial ischemia, and this stress can even trigger acute coronary syndromes or sudden cardiac death. Therefore, for the first time, this study aimed to investigate the method for establishing a rat model of myocardial ischemia with psychological stress and its evaluation.

Forty male Wistar rats were randomly divided into the sham (S, n=10), myocardial infarct (MI, n=10), psychological stress (MODEL, n=10), and myocardial infarct with psychological stress (MI + MODEL, n=10) groups. The rat model of psychological stress was established by measuring the data from activity restriction for 6 hours and followed by tail clamp stimulation for 5 minutes every day for 14 days. The rat model of the myocardial infarct with psychological stress was established by occluding the left coronary anterior descending artery in the MODEL rats. The body weight of rats was measured daily, the behavior parameters were evaluated via open-field test and elevated plus-maze, tongue color and sublingual vein were observed, rats' acral blood flow perfusion was detected by PIM II (Perfusion Imager II), mesenteric microcirculation was measured by capillaroscopy, and hemodynamics was measured by a polygraph system. An automatic biochemical analyzer determined the content of serum cTnT (cardiac troponin T), Hcy (homocysteine), and activity of LDH (lactate dehydrogenase). Myocardial infarct size was measured with TTC (triphenyhetrazolium chloride) staining.

We found that rats in the psychological stress (MODEL) group were characterized by coarse hair, dark mucosa of the lips and claw, low spirit, decreased body weight, and increased anxiety. Compared with rats in the sham group, rats in the MODEL + MI group showed decreased mesenteric blood flow, narrowed arteriole and venule diameter, reduced acral blood flow perfusion, and LV ±dp/dt_max (the maximal rate of the increased and decrease of left ventricular pressure), as well as increased serum content of cTnT, Hcy, and LDH activity. Compared with the MI group, rats in the MODEL + MI group showed deteriorated microcirculation dysfunction manifested as a dark tongue color of deep purple, prominently extended and varicose sublingual vein, and aggravated myocardial damage in the form of increased infarct size and LDH leakage.

In conclusion, the rat model of myocardial ischemia with psychological stress was successfully established, and manifested as aggravating behavioral disorder, mesenteric microcirculation and left ventricular dysfunction, and myocardial damage.