Dalargin, a peripheral opiate receptor agonist, in the pathogenesis of myocardial contusion in rats with different stress tolerance

Aim . To evaluate the effect of dalargin, a peripheral opiate receptor agonist, on the adaptive strategy of rats with different stress tolerance after the myocardial contusion. Materials and Methods. The experiment was performed on 216 male rats weighing 250-300 g which were ranked according to stress resistance using the forced-swim (Porsolt) test and the open feld test. Rats were divided into 3 groups: control animals and those with a blunt cardiac injury, with or without dalargin administration (100 µg/kg intramuscularly 2 hours before anesthesia, immediately before injury, and 2 hours post injury). Each group included 3 subgroups (n = 8 rats per each) with high, medium, and low stress tolerance. Myocardial contusion was simulated using an original device. Blood levels of glucose, lactic acid, triglycerides, corticosterone, total protein, albumin, white blood cell count, reduced glutathione and total antioxidant capacity were measured in all rats 24 hours post injury. Results . Myocardial contusion altered the metabolic profle to the stress-related pattern. The most signifcant increase in rectal temperature, white blood cell count, corticosterone, glucose, lactic acid, and triglyceride levels as well as maximum decrease in reduced glutathione and total myocardial antioxidant capacity were documented in animals with low stress tolerance. Administration of dalargin alleviated the stress response regardless of animal stress resistance. Conclusion . Blunt cardiac injury and myocardial contusion induce stress response characterised by hypercatabolism, systemic infammatory response syndrome, and myocardial oxidative stress in all rats, with a most signifcant response in animals with low stress tolerance. A peripheral opiate receptor agonist dalargin did not change the response pattern but curbed the stress response.