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.

Opposite changes in cardiac chronotropy induced by selective blockade of α(1A)-adrenoceptors in rats of different age.

Selective blocker of α(1A)-adrenoceptors WB4101 induced changes in heart rate in rats: it caused bradycardia in 3-, 6-, or 20-week-old rats (severity of bradycardia increased with increasing animal age) and increased heart rate in newborn rat pups.

Indicators of trace-element status of children living in rural areas.

The content of essential and toxic elements, except beryllium and mercury, in the hair of examined children (girls aged 7-9 years) is within the biologically acceptable levels set by WHO. The data on the content of essential trace elements suggest that urgent measures aimed at normalization of the elemental status of children are required.

ATP as modulator of carbacholine effect on contractility of rat myocardium in postnatal ontogeny.

We studied combined effect of 2-m-ATP, P(2) receptor agonist, and carbacholine, muscarinic M(2) cholinoreceptor agonist, on contractility of rat myocardium during the postnatal ontogeny. Activation of P(2) receptors can stimulate or attenuate the effects of carbacholine depending on animal age. 2-m-ATP potentiates the inhibitory effect of carbacholine on myocardial contractility in 14- and 100-day-old rats.

Role of P2X receptors in positive inotropic effect of rat myocardium during ontogeny.

Experiments with selective agonists and antagonists of purinoceptors allowed us to evaluate the subtype of P2X receptors. We showed that the myocardium of 14- 100-day-old rats contains functionally active P2X1 receptors. These receptors are involved in the realization of the positive inotropic effect of the atria and ventricles.

Age-related peculiarities of contractile activity of rat myocardium during blockade of hyperpolarization-activated currents.

Contractile activity of atrial and ventricular myocardial strips isolated from rats of various age was examined under conditions of blockade of non-selective hyperpolarization-activated cation currents. Addition of ZD7288, a blocker of non-selective hyperpolarization-activated cation currents, to the perfusion solution increased the contraction force of atrial and ventricular strips in 1-, 8-, and 20-week rats, but produced an opposite effect on contractile activity of atrial and ventricular strips in 3-week rats.

M3 cholinergic receptors are involved in postnatal development of cholinergic regulation of cardiac activity in rats.

We studied the role of M3 cholinergic receptors in the regulation of cardiac activity in rats during early postnatal ontogeny in vivo. Blockade of M3 cholinergic receptors in 20-week-old animals increased heart rate and decreased blood pressure. In rats aging 8, 6, and 3 weeks, blockade of M3 cholinergic receptors had little effect on R-R interval, but unexpectedly increased it in 1-week-old animals.

Parasympathetic cardiac effects in sympathectomized rats.

In adult sympathectomized rats the right and left vagus nerves exhibited asymmetric effects on heart rate and strength of cardiac contractions. After vagotomy, the heart rate and stroke volume remained high in sympathectomized rats, but returned to normal in intact animals. The sympathetic nervous system plays a role in postvagotomic tachycardia.

Effect of ATP and its analogs on contractility of rat myocardium during ontogeny.

The effects of P2-receptor agonists on myocardial contractility were examined in rats aging 14-100 days. ATP and its stable analog 2-methylthio-ATP potentiated the contraction force of isolated myocardial strips in a dose-dependent manner. The agonist concentrations producing the positive inotropic effect increased from days 14 to 100 of life.

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.