The effect of adenosine on the function of the heart in Octopus vulgaris was studied using an isolated heait preparation. Bolus injections of adenosine or AMP (adenosine precursor) induced both positive chronotropic and inotropic effects. The maximum inotropic effect preceded the maximum chronotropic effect. The impermeable adenosine analogue 2-chloroadenosine elicited a similar effect, while t...

Objective(s): Recently, we showed that some new synthetic compounds structurally related to cilostamide (4-(1,2-dihydro-2-oxoquinolin-6-hydroxy)- N-cyclohexyl-N-methylbutanamide), a selective phosphodiesterase 3 (PDE3) inhibitor, produce inotropic effect comparable to that of IBMX (3-isobutyl-1-methylxanthine), a non-selective PDE inhibitor, but with differential chronotropic effect. In this in...

During development, the cardiac alpha 1-adrenergic chronotropic response changes from positive in the neonate to negative in the adult. The negative chronotropic effect of alpha 1-adrenergic stimulation in the adult depends on maturation of sympathetic innervation and the presence of a pertussis toxin (PT)-sensitive guanine nucleotide-binding (G) protein. To examine the possibility of a develop...

The purpose of these experiments was to determine whether muscarinic cholinergic agonists exerted a negative chronotropic effect in the absence of endogenous norepinephrine in isolated guinea pig ventricular myocardial strips. The chronotropic response to physostigmine (10(-6) M) in control, reserpine-pretreated animals, and in the presence of increased norepinephrine release induced by superfu...

BACKGROUND Chronic renal failure is frequently associated with a high risk of sudden cardiac death due to dysfunction of the autonomic nervous system. The pathogenic mechanisms underlying the parasympathetic cardiac dysautonomia are not fully elucidated yet. METHODS Chronic renal failure was induced in rats by 5/6 nephrectomy. Blood pressure, resting heart rate and plasma levels of creatinine...

We studied the effects of intense sympathetic stimulation on the chronotropic responses of the heart to subsequent test stimulations of the cardiac autonomic nerves in dogs anesthetized with a-chloralose. Such intense sympathetic stimulations (which we refer to as "release stimulations") are known to release neuropeptide Y as well as norepinephrine. The changes in cardiac cycle length evoked by...

1. An in.situ heart preparation was used to evaluate cardiac performance in the sea raven, Hemitripterus americanus, under physiological inflow and outflow pressure conditions. Winter and summer fish were subjected to an acute 10 °C temperature change from the seasonal ambient value. The maximum cardiac output (Vb) under each temperature condition was determined by altering inflow pressure to t...

Acetylcholine is directly perfused into the canine sinus node in vivo through its cannulated nutrient artery. After atropinization, the chronotropic action from intranodal administration of acetylcholine was identical to that of control injections of Ringer's solution alone. Eserine produced only a negative chronotropic action before, and no significant action after, atropinization. Direct perf...

Modgil A, Zhang Q, Pingili A, Singh N, Yao F, Ge J, Guo L, Xuan C, O’Rourke ST, Sun C. Angiotensin-(1–7) attenuates the chronotropic response to angiotensin II via stimulation of PTEN in the spontaneously hypertensive rat neurons. Am J Physiol Heart Circ Physiol 302: H1116–H1122, 2012. First published December 23, 2011; doi:10.1152/ajpheart.00832.2011.—Several studies have focused on the benefi...