Role of 5-HT(2B) Serotonin Receptor Agonist in the Regulation of Pumping Function of the Heart.

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.

Regulation of pumping function of the heart in developing body under changing regimens of motor activity.

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.

[Effect of the sharply strengthened motor activity on heart pumping ability of rats and mechanisms of its regulation].

The indicators of heart pumping ability of rats at a muscular loading of the maximum power and also in the conditions of transition from sharply strengthened motor activity regime on a strengthened motor activity regime at adrenergic influence stimulation and blockade were investigated. At rats of 100-daily age at the strengthened motor activity heart rate is less, and blood stroke volume is more, than in the rats, subject to muscular loading of the maximum power. The adrenergic influence on the heart's pumping ability of sharply strengthened motor activity rats is much more, than of unlimited motor activity rats.

Influence of 5-HT(2) receptor agonist on cardiac pumping function of trained offspring of trained rats.

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.

Peculiarities of regulation of heart rate and stroke volume in rats during ontogeny.

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.