Blood-letting of 450 to 1,000 ml with or without saline infusion was performed in dogs. In some dogs, right atrial pacing was carried out during blood-letting. Heart rate and isometric time-tension index were measured as the indicators of chronotropism and inotropism, respectively. After 60 min of blood-letting, dogs were sacrificed and mitochondria were isolated from the left ventricular myoca...

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Chronotropic incompetence (CI) is defined as the inability to reach 80% expected reserve frequency for age during exertion, and it frequently observed in stress tests patients undergoing cardiac rehabilitation programs due a combination factors, that include use betablockers. Despite theoretical basis suggesting lower...

Ch ro not ropic and inotropic effects of glucagon were compared with those of norepinephrine using the excised SA node and the papillary muscle preparations cross-circulated with a donor dog. Glucagon was administered i.v. to the donor dog at doses of I to 30 μg/kg, which caused a marked chronotropic but less marked inotropic effect. Cardiohemodynamic response to glucagon of anesthetized dog...

decreased cardiac responsiveness to adrenergic stimulation has been observed in cholestatic liver disease, but the cause remains unclear. previous reports have suggested that nitric oxide overproduction might have a role in cholestasis-induced bradycardia via inhibition of l-type calcium channels. in the present study, the digoxin has been used to increase cardiac ca2+ transient in male sprague...

The dorsomedial hypothalamus (DMH) and lateral/dorsolateral periaqueductal gray (PAG) are anatomically and functionally connected. Both the DMH and PAG depend on glutamatergic inputs for activation. We recently reported that removal of GABA-ergic tone in the unilateral DMH produces: asymmetry, that is, a right- (R-) sided predominance in cardiac chronotropism, and lateralization, that is, a gre...

THYROID HORMONES AND THE CARDIOVASCULAR SYSTEM According to the classical literature on human physiology4, thyroid hormones – thyroxine (T4) and triiodothyronine (T3) – produce an overall increase in the basal metabolism of the human body. This is accompanied by greater tissue oxygen consumption, owing both to vasodilation and the concomitant increase in cardiac output, which are facilitated by...

Both bethanechol and physostigmine produced dose-dependent negative chrono-, dromo- and inotropic effects in the dog isolated atrial preparation. Within a relatively small dose of bethanechol and physostigmine, negative inotropic effect was clearly induced but no significant chrono- and dromotropic changes were observed. With a relatively large dose, the two cholinomimetics caused negative chro...

Spontaneously beating isolated atria of rabbits responded to Mn++ and Co++ with a progressively increasing negative chronotropism and inotropism, which was reversible by washout and by elevating the bath concentration of Ca++. The cumulative dose response curve for adrenaline for chronotropic response was markedly shifted to the right in the presence of Mn++ or Co++. This effect was also revers...