Using 10 isolated, blood-perfused canine atrial, and ventricular preparations, the effects of d- and l-verapamil on SA nodal pacemaker activity and contractility were investigated. l-verapamil and d-verapamil produced dose-related negative chronotropic and inotropic effects in all experiments. l-verapamil was approximately 10 time more potent than d-verapamil both in inotropism and chronotropis...

Tadayoshi Miyamoto, Toru Kawada, Yusuke Yanagiya, Tsuyoshi Akiyama, Atsunori Kamiya, Masaki Mizuno, Hiroshi Takaki, Kenji Sunagawa, and Masaru Sugimachi Department of Physical Therapy, Faculty of Health Sciences, Morinomiya University of Medical Sciences; and Department of Cardiovascular Dynamics, Advanced Medical Engineering Center, and Department of Cardiac Physiology, National Cardiovascular...

BACKGROUND Physiological reflexes modulated primarily by the vagus nerve allow the heart to decelerate and accelerate rapidly after a deep inspiration followed by rapid movement of the limbs. This is the physiological and pharmacologically validated basis for the 4-s exercise test (4sET) used to assess the vagal modulation of cardiac chronotropism. OBJECTIVE To present reference data for 4sET...

The reported circadian rhythm of blood pressure variability with a rise in pressure before awakening has been the subject of controversy. Previous studies have suggested that since heart rate continues to fall before awakening while blood pressure is rising these physiological variables are subject to different control mechanisms. To evaluate further the dissociation of heart rate and blood pre...

Cardiovascular function was studied in anaesthetised male rats which received 50 micrograms/ml of arsenic (as sodium arsenate) in deionised drinking water for 320 days. High urinary excretion of arsenic was found at the end of treatment and the metal accumulated considerably in the kidneys and liver, which both presented slight alterations. No histopathological modifications were evident in oth...

Adenosine is released from the myocardium in response to a decrease in the oxygen supply/demand ratio, as is seen in myocardial ischemia; its protective role is manifested by coronary and collateral vessel vasodilation that increase oxygen supply and by multiple effects that act in concert to decrease myocardial oxygen demand (i.e., negative inotropism, chronotropism, and dromotropism). During ...

Rhinella icterica is a Brazilian toad with parotoid secretion that toxic to insects. In this work, we examined the entomotoxicity of in locust (Locusta migratoria) semi-isolated heart and oviduct preparations vitro. The caused negative chronotropism (at highest dose tested: 500 μg) markedly enhanced amplitude spontaneous contractions tonus muscle (0.001–100 μg). addition, neurally-evoked muscle...

We hypothesized that absence of the 5-HT(1A) receptor would negatively affect the development of cardiorespiratory control. In conscious wild type (WT) and 5-HT(1A) receptor knockout (KO) mice, we measured resting ventilation (Ve), oxygen consumption (Vo(2)), heart rate (HR), breathing and HR variability, and the hypercapnic ventilatory response (HCVR) at postnatal day 5 (P5), day 15 (P15), and...

Atrial fibrillation (AF) is the most common cardiac arrhythmia facing physicians, afflicting 13% of men and 11% of women over 85 years of age. Epidemiological studies estimate that there are ≥ 11 million AF sufferers in the seven major economies and that its prevalence will increase two- to threefold over the next 50 years. Current strategies for treating AF involve either sinus rhythm (SR) mai...