Electron paramagnetic resonance study of nitric oxide production during 5-HT2 receptor blockade in the blood, heart, and liver of rats with myocardial infarction

The effect of serotonin 5-HT2 receptor blockade on nitric oxide production in rats with myocardial infarction was evaluated by the method of electron paramagnetic resonance. The spectra were recorded in samples of the heart tissue (left and right chambers), liver, and blood. 5-HT2 receptor blockade during myocardial infarction was followed by a decrease in the total content of nitrosyl complexes in the spin trap and R and T conformers of Hb-NO. The percent of T conformers increased in the remaining complexes of Hb-NO. These changes were observed in the heart and, particularly, in the blood. The amount of spin-trap complexes was lower in the liver. Hence, nitric oxide molecules were primarily associated with the spin trap in liver tissue. The decrease in the number of Hb-NO complexes in the blood probably reflects the decrease in the severity of hypoxia due to myocardial infarction. A correlation was found between these changes and physiological state of rats. 5-HT2 receptor antagonist improved general state of rats with infarction and increased survival rate.