The effect of α-methyl-5-hydroxytryptamine maleate, an agonist of 5-HT2B serotonin receptors, on the pumping function of the heart was examined in rats with forced motor behavior. At rest, swim-trained rats demonstrated lower HR and greater stroke volume and cardiac output than untrained rats. The agonist decreased HR, stroke volume, and cardiac output in 21- and 70-day-old swim-trained rats, but not in 100- and 200-day-old rats.
Aim. The purpose of the article is to study the patterns of forming heart pumping function reserves in schoolchildren in the conditions of hypo- and hyperkinesia. Materials and methods. The heart pumping function was assessed with the help of Ergoracer cycle ergometer (Kettler) and the load adjusted using ERGO-KONZEPT software developed for this equipment. Reserves were established by the difference between the indicators of the heart pumping function: heart rate, stroke volume, minute blood flow at maximum load and at rest. The peculiarities of heart pumping function reserves were studied in the conditions of adaptation to different movement modes in schoolchildren aged 7–18 years. Results. It was established that heart reserves in terms of heart contractions increase with age mainly by lowering the frequency at rest. Heart reserves in terms of stroke volume and minute blood flow also increase with age, especially in trained persons. The nature of changes in the reserves of minute blood flow coincides with the pattern of changes in heart reserves in terms of stroke volume. Conclusion. The study of heart reserves allowed to find the peculiarities of changes in the chronotropic and inotropic responses of the heart, which were established as the difference between heart rate frequency, stroke volume, and minute blood flow at maximum stress and the data obtained at relative rest during adaptation to different movement modes.
Changes in heart rate and stroke volume after successive blockade of cardiac adreno- and cholinoceptors were examined on rats of different age. It was established that irrespective of animal age the heart rate remained unchanged under conditions of total adreno- and cholinergic blockade of the heart. Stroke volume under conditions of total adreno- and cholinergic blockade increased with age.
We analyzed parameters of the pumping function of the heart in rats subjected to enhanced motor activity after a preliminary 70-day hypokinesia under conditions of α- and β-adrenergic receptor stimulation with norepinephrine followed by blockade of β-adrenergic receptor with propranolol (obsidian) and α1-adrenergic receptors with doxazosin. After norepinephrine administration, the HR and cardiac output were higher in rats with enhanced physical activity after preliminary hypokinesia than in rats with low physical activity. After propranolol administration, stroke volume and cardiac output in 100-day-old rats with limited activity were lower, and HR higher was than in rats with enhanced physical activity after preliminary 70-day hypokinesia. After administration of doxazosin, rats with limited motor activity demonstrated more pronounced changes in HR than rats with enhanced physical activity after preliminary 70-day hypokinesia.
We studied cardiac pumping function in the offspring of rats subjected to swimming exercise and the offspring of untrained rats. The rat pups were adapted for swimming with stepwise increasing load from day 21 to 70 life. At the age of 21 and 70 days, offspring of trained rats showed lower HR and significantly higher stroke volume and cardiac output than offspring of untrained rats. Agonist of 5-HT(2)-receptors α-methyl-5-hydroxytryptamine maleate (30 μg/kg) reduced enhanced stroke volume in trained offspring born by trained mothers. In trained offspring of untrained rats, the agonist had more pronounced effect on HR.
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