title: Vagal stimulation attenuates sympathetic enhancement of left ventricular function.
abstract: We studied the effects of stimulation of the vagal and sympathetic cardiac nerves on left ventricular contraction and relaxation in 16 anesthetized dogs. In each experiment, we paced the ventricles at a fixed rate of 120 beats/min, and we kept the systemic arterial pressure constant. We used the maximum rates of left ventricular pressure rise (dP/dtmax) and fall (dP/dtmin) as our indexes of ventricular contraction and relaxation. Sympathetic nerve stimulation at a frequency of 6 Hz increased dP/dtmax by 802 mmHg/s and raised dP/dtmin by 847 mmHg/s above the control level. The effect of vagal nerve stimulation was directly dependent on the level of sympathetic stimulation. In the absence of sympathetic stimulation, vagal nerve stimulation at a frequency of 5 Hz decreased dP/dtmax by 187 mmHg/s and reduced dP/dtmin by 199 mmHg/s below the control level. When the sympathetic stimulation was 6 Hz, vagal nerve stimulation at 5 Hz decreased dP/dtmax by 513 mmHg/s and reduced dP/dtmin by 709 mmHg/s. Furthermore, propranolol, in doses of 1.5 mg/kg, abolished any significant vagal effect on ventricular contraction or relaxation. We conclude that combined sympathetic-vagal stimulation results in a substantial antagonistic interaction such that vagal stimulation significantly attenuates the sympathetic enhancement of left ventricular function.
authors.affiliation: Division of Investigative Medicine, Mt. Sinai Medical Center.
authors.forename: R J
authors.initials: RJ
authors.lastname: Henning
authors.forename: I R
authors.initials: IR
authors.lastname: Khalil
authors.forename: M N
authors.initials: MN
authors.lastname: Levy
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D004285:Dogs; D004558:Electric Stimulation; D006321:Heart / Q000502:physiology*; D006329:Heart Conduction System / Q000502:physiology; D006352:Heart Ventricles; D009200:Myocardial Contraction; D010275:Parasympathetic Nervous System / Q000502:physiology; D011312:Pressure; D011433:Propranolol / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D011433:Propranolol