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.