Related Experiment Video
Updated: May 2, 2026
14:02
Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
24.1K
Interstitial ATP and norepinephrine concentrations in active muscle.
Jianhua Li1, Nicholas C King, Lawrence I Sinoway
1Division of Cardiology, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 University Dr, Hershey, PA 17033, USA. jzl10@psu.edu
Circulation
|May 25, 2005
Summary
Exercise increases sympathetic nervous system activity. In active muscle, elevated interstitial adenosine triphosphate (ATP) stimulates P2X receptors on sympathetic nerves, increasing norepinephrine (NE) release and maintaining blood pressure.
Area of Science:
- Physiology
- Neuroscience
- Biochemistry
Background:
- Sympathetic nervous system activity and norepinephrine (NE) are crucial for maintaining blood pressure during exercise.
- Contracting skeletal muscle releases adenosine triphosphate (ATP), and sympathetic nerves possess P2X receptors.
Purpose of the Study:
- To investigate if elevated interstitial ATP in skeletal muscle stimulates P2X receptors, thereby increasing interstitial NE concentrations.
- To test the hypothesis that ATP acts as a signaling molecule between contracting muscle and sympathetic nerves.
Main Methods:
- Microdialysis was used to collect interstitial fluid from rat skeletal muscle.
- High-performance liquid chromatography (HPLC) measured concentrations of ATP and NE.
- Experiments involved muscle stretch, intra-arterial ATP injection, and administration of P2X receptor antagonist (PPADS) and nucleotidase inhibitor (ARL67156).
Main Results:
- Muscle stretch significantly increased interstitial ATP ([ATP]i) and NE ([NE]i) levels.
- The increase in [NE]i was directly correlated with the rise in [ATP]i.
- ATP administration elevated [NE]i, an effect modulated by PPADS and ARL67156, confirming P2X receptor involvement.
Conclusions:
- Skeletal muscle releases ATP during contraction, which stimulates P2X receptors on sympathetic nerves.
- This ATP-mediated signaling increases interstitial NE concentrations, contributing to blood pressure regulation during exercise.
Related Concept Videos
01:26Cross-bridge Cycle
108.8K
As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
108.8K
01:25Energy Supply for Muscle Contraction
5.3K
Skeletal muscle fibers have the unique ability to switch between rest and contraction states, using different sources of ATP for energy. The contraction cycle and Ca2+ transport back into the sarcoplasmic reticulum for relaxation require significant ATP. However, the ATP reserves in muscle fibers are limited and can only sustain contractions for a few seconds. Additional ATP production becomes necessary for prolonged contractions. As a result, muscle fibers generate ATP through various sources,...
5.3K
01:24Muscle Recovery and Fatigue
4.4K
Muscle fatigue refers to the decline in a muscle's ability to maintain the force of contraction after prolonged activity. It primarily stems from changes within muscle fibers. Even before experiencing muscle fatigue, one may feel tired and have the urge to stop the activity. This response, known as central fatigue, occurs due to changes in the central nervous system, namely the brain and spinal cord. While there is no single mechanism that induces fatigue, it may serve as a protective...
4.4K
01:20Motor Unit Stimulation
4.7K
When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
4.7K
01:27Exercise and Muscle Performance
6.2K
Exercise induces a range of adaptations in muscle tissue, depending on the type and duration of activity. Such physical training can be broadly categorized into two types: endurance exercises and resistance exercises.
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
6.2K
01:25Smooth Muscle Contraction
8.7K
Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
8.7K