Related Experiment Video
Updated: May 4, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
[Effects of exhaustive exercise on contractile responses mediated by beta-adrenoceptor in rat cardiac myocytes]
Li-Ping Gao1, Ying Liu1, Hong Sun1
1Department of Physiology, Xuzhou Medical College, Xuzhou 221002, China.
Objective:
To investigate the effects of exhaustive exercise on contraction mediated by beta-adrenoceptor (beta-AR) in rat cardiac myocytes and to analyze the mechanism by which cardiac systolic dysfunction is caused after exhaustive exercise.
Methods:
Sixteen SD rats were divided randomly into sedentary group and trained group. Cardiac myocytes were isolated from sedentary group and trained group after five times of exhaustive exercise in one week. Shortening response to norepinephrine (NE), time-to-peak contraction (TTP) and time-to-95% relaxation (R95) were measured after alpha1-AR were blocked. Also shortening responses to different levels of NE were observed.
Results:
Shortening amplitudes in trained rat cardiomyocytes were lower than that in sedentary group. Compared with sedentary group, shortening amplitudes induced by beta-AR stimulation were significantly decreased, meanwhile TTPs and R95 were prolonged when beta-AR were activated in trained rat cardiomyocytes. beta-AR responsiveness to NE was weakened in trained group compared with that in sedentary group.
Conclusion:
Decreased shortening cardiomyocyte systolic function stimulating by beta-AR could result in cardiac systolic dysfunction after exhaustive exercise.
Related Concept Videos
Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors...
Heart Failure Drugs: β-Blockers
Antihypertensive Drugs: Action of β1 Blockers
Pathophysiology of Cardiac Performance
Exercise and Cardiovascular Response
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
Heart Failure II: Pathophysiology

