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Journals and Conferences
Cyclic GMP was applied to the rabbit right auricle by a cut-end method. The nucleotide decreased the spontaneous rate, hyperpolarized the cell membrane and reduced the amplitude and the slow component of the action potential. It also decreased the force of contraction. These results suggest that cGMP may be the mediator of the action of acetylcholine in the… (More)
The effects of intracellular application of noradrenaline, acetylcholine, cAMP and cGMP were studied in the sinus·node of the rabbit. Noradrenaline and acetylcholine were without effect on electrical activity. In about one third of cases, cAMP increased, and cGMP decreased the slope of slow depolarization. These results suggest that adrenergic as well as… (More)
Propranolol introduced by a cut-end method into atrial trabeculae evoked negative inotropic response without any significant changes in basic electrical parameters. This effect was resistant to noradrenaline but not to dibutyryl cAMP. These results suggest that existence of intracellular beta adrenoreceptors involved in the control of the contraction.
A strip of tissue cut from the sinus node, 0.5 mm wide, was studied in a sucrose gap chamber. With the gap width of 0.6–1.5 mm the 2 ends of the preparation showed nonsynchronous activity. Synchronization could be re-established by a shunt resistor, 15–100 kΩ, connected a cross the gap, suggesting that synchronous firing of the sinus node requires local… (More)
Trans-gap application of noradrenaline or acetylcholine evoked pronounced inotropic but no chronotropic effects in spontaneously active rabbit auricle preparations. These results suggest the existence of intracellular receptors, both adrenergic and cholinergic, which were involved in the control of auricular contraction.
Dibutyryl cGMP, like acetylcholine, shortens and reduces repolarization and overshoot of the action potential, slightly hyperpolarizes the cell and decreases the force of the contraction in the atrial working muscle. It suggests that cGMP may mediate the action of acetylcholine in the atrial working fibres.
BACKGROUND Histamine is one of the biologically active substances that activate adenyl cyclase enzymatic system through H2 receptor. The aim of the study is demonstration of the presence of membranous histamine receptors in cardiomyocytes and determination of their role in function of the cardiac muscle cell. MATERIAL AND METHODS The experiments were… (More)
Verapamil stops the electrical activity of the sinus node cells. In the presence of verapamil, dibutyryl cAMP brings about a recovery of the spontaneous activity, whereas noradrenaline is ineffective.
Isotonic solution of cAMP-Na was applied into spontaneously beating auricular fibres by a cut-end method. Cyclic AMP enhanced the spontaneous rate (mean 48%) and increased the contractile tension (mean 297%). These results provided direct evidence that cAMP is involved in the spontaneous activity and contraction in the heart muscle.