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Caffeine keeps you awake by blocking adenosine receptors. Each type of adenosine receptor has different functions, although with some overlap. [3] For instance, both A 1 receptors and A 2A play roles in the heart, regulating myocardial oxygen consumption and coronary blood flow, while the A 2A receptor also has broader anti-inflammatory effects throughout the body. [4]
The actions of the A 2A receptor are complicated by the fact that a variety of functional heteromers composed of a mixture of A 2A subunits with subunits from other unrelated G-protein coupled receptors have been found in the brain, adding a further degree of complexity to the role of adenosine in modulation of neuronal activity.
Upregulation of receptors, on the other hand, can result in super-sensitized cells, especially after repeated exposure to an antagonistic drug or prolonged absence of the ligand. Some receptor agonists may cause downregulation of their respective receptors, while most receptor antagonists temporarily
Adenosine A 3 receptors are G protein-coupled receptors that couple to Gi/Gq and are involved in a variety of intracellular signaling pathways and physiological functions. It mediates a sustained cardioprotective function during cardiac ischemia, it is involved in the inhibition of neutrophil degranulation in neutrophil-mediated tissue injury, it has been implicated in both neuroprotective and ...
These receptors enable the regulation of multiple processes such as cell proliferation, differentiation, function, and death. [47] The activation of the adenosine A1 receptor is required for osteoclast differentiation and function, whereas the activation of the adenosine A2A receptor inhibits osteoclast function. The other three adenosine ...
Downregulation of protein kinase A occurs by a feedback mechanism and uses a number of cAMP hydrolyzing phosphodiesterase (PDE) enzymes, which belong to the substrates activated by PKA. Phosphodiesterase quickly converts cAMP to AMP, thus reducing the amount of cAMP that can activate protein kinase A. PKA is also regulated by a complex series ...
Purine metabolites: Nucleotides (e.g., ATP) and nucleosides (e.g., adenosine) that have reached the extracellular space can also serve as danger signals by signaling through purinergic receptors. [30] ATP and adenosine are released in high concentrations after catastrophic disruption of the cell, as occurs in necrotic cell death. [31]
Adenosinergic means "working on adenosine". An adenosinergic agent (or drug) is a chemical which functions to directly modulate the adenosine system in the body or brain. Examples include adenosine receptor agonists, adenosine receptor antagonists (such as caffeine), and adenosine reuptake inhibitors.