Adrenoceptor-mediated changes of excitation and contraction in ventricular heart muscle from guinea-pigs and rabbits

• Published in: The Journal of physiology Vol. 397; no. 1; pp. 657 - 670
• Main Authors: Hescheler, J, Nawrath, H, Tang, M, Trautwein, W
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01.03.1988; Blackwell
• Subjects: Action Potentials - drug effects; alpha -adrenergic; Animals; Biological and medical sciences; Biomechanical Phenomena; Calcium - physiology; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Heart; In Vitro Techniques; Ion Channels - drug effects; Isoproterenol - pharmacology; membrane currents; Myocardial Contraction - drug effects; Norepinephrine - pharmacology; Phenylephrine - pharmacology; Propranolol - pharmacology; Rabbits; Receptors, Adrenergic - physiology; ventricle; Ventricular Function; Vertebrates: cardiovascular system; Heart; Transmembrane current; Vertebrata; Mammalia; Calcium; α-Adrenergic receptor; Electrophysiology; Circulatory system; Membrane potential; Muscle contraction
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1988.sp017024

1. The influence of alpha-adrenoceptor stimulation on mechanical and electrophysiological parameters was investigated in ventricular preparations from guinea-pigs and rabbits. Action potential and force of contraction were measured in papillary muscles and ionic currents were measured in isolated myocytes. 2. The effects of alpha-adrenoceptor stimulation were compared with those of beta-adrenoceptor stimulation. 3. In the guinea-pig the stimulation of alpha-adrenoceptors caused a small increase in the force of contraction (less than 10% of the response to beta-adrenoceptor stimulation) which was not accompanied by any increase of the slow calcium inward current. beta-Adrenoceptor stimulation produced large increases in both force of contraction and slow inward calcium current. The noradrenaline-induced increase in the slow inward calcium current was not affected by phentolamine. 4. In the rabbit, alpha-adrenoceptor stimulation produced large increases in the force of contraction (about two thirds of those seen in response to beta-adrenoceptor stimulation). Whereas beta-adrenoceptor stimulation also produced large increases in both maximal upstroke velocity of slow-response action potentials and slow inward calcium current, there was almost no change of both parameters in response to alpha-adrenoceptor stimulation. 5. We conclude that, first, the contribution of alpha-adrenoceptors to adrenoceptor-mediated changes of force of contraction is minimal in the guinea-pig ventricle, and second, the pronounced changes of force of contraction in the rabbit ventricle in response to alpha-adrenoceptor stimulation are unrelated to changes in the slow inward calcium current.