Age-related peculiarities of inotropic response of rat myocardium to selective block of M1-cholinoreceptors

Effect of NO Synthase Blockade on Myocardial Contractility of Hypokinetic Rats during Stimulation of β-Adrenoreceptors

Stimulation of β-adrenoreceptors with low (10(-8) and 10(-7) M) or high (10(-6) M) doses of isoproterenol in hypokinetic rats treated with L-NAME (a non-selective blocker of NO synthases) decreased or increased myocardial contractility, respectively. In control rats, all examined doses of isoproterenol used under blockade of NO synthases inhibited myocardial contractility.

Effect of NO synthase blockade on NO production in rat heart under conditions of hypokinesia

Electron paramagnetic (EPR) spectroscopy study showed that 90-day hypokinesia in rats is accompanied by an increase in NO production in the heart. A nonselective NO synthase inhibitor L-NAME decreased the content of NO in the heart atria and ventricles of hypokinetic rats by 67-70%. A selective inhibitor of inducible NO synthase, aminoguanidine, also decreased the level of NO in the heart atria and ventricles of hypokinetic rats by 60-65%. Our results indicate that the increase in NO production during hypokinesia is associated with activation of NO synthases.