Related Experiment Video
Updated: Aug 15, 2026
Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
Postnatal developmental changes in the electrophysiological properties of cat right ventricular papillary muscles
Insights
Cat heart muscle cells show significant electrophysiological development after birth. Key properties like action potential duration mature throughout early postnatal life, impacting cardiac function.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Cellular Electrophysiology
Background:
- Cardiac electrophysiology is crucial for heart function.
- Understanding postnatal development of myocardial electrophysiology is vital for pediatric cardiology.
- Previous research has not fully elucidated age-related electrophysiological changes in feline right ventricular papillary muscles.
Purpose of the Study:
- To investigate the electrophysiological properties of cat right ventricular papillary muscles during postnatal development.
- To determine how resting membrane potential, action potential characteristics, and conduction velocity change with age.
- To examine the influence of extracellular calcium, potassium, and ouabain on myocardial electrophysiology across different developmental stages.
Main Methods:
- Intracellular microelectrode recordings were performed on cat right ventricular papillary muscles.
- Animals were studied at three developmental stages: neonatal, infant, and adult.
- Experiments involved varying extracellular ion concentrations ([Ca]o, [K]o) and drug exposure (ouabain) while measuring electrophysiological parameters.
Main Results:
- Resting membrane potential, action potential amplitude, Vmax, and action potential duration significantly increased with age.
- Conduction velocity also showed a significant age-dependent increase.
- Responses to altered [Ca]o and ouabain were more pronounced in infant and adult tissues compared to neonatal tissues, suggesting developmental changes in ion channel function.
Conclusions:
- The electrophysiological properties of the cat myocardium undergo significant development during early postnatal life.
- Age-related changes in action potential duration are independent of stimulation frequency.
- These developmental shifts in electrophysiology are likely related to concurrent changes in cardiac morphology and transmembrane ionic gradients.
Abstract:
Cellular electrophysiological properties of cat right ventricular papillary muscles were studied during postnatal development using intracellular microelectrodes. Animals were studied in the neonatal period (less than 75 h of age), in infancy (16 to 18 days old) and in adult life (1.8 to 2.3 kg body weight). Resting membrane potential, action potential amplitude, Vmax and action potential duration increased significantly with age. The age related changes in action potential duration were independent of stimulation frequency. Conduction velocity was measured using two simultaneous impalements and increased significantly with age. Exposure to low [Ca]o (0.2 mmol X litre-1) caused a prolongation in action potential duration which was greater in infant and adult than neonatal myocardium, and was greatest at low stimulation frequencies. High [Ca]o shortened action potential duration and this was also greater in infant and adult tissue. Action potential duration was prolonged by low [K]o (0.5 mmol X litre-1) and shortened by high [K]o. Both of these effects appeared to be independent of age. Exposure to ouabain, 10(-8) and 10(-7) mol X litre-1 caused a dose related shortening of action potential duration. This effect was significantly greater in adult and infant than neonatal myocardium. The results indicate that the electrophysiological properties of the cat myocardium continue to develop during early postnatal life. These findings are discussed in relation to changes in morphology and transmembrane ionic gradients occurring at this time.
