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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]
Furthermore, located in the intracellular side close to the membrane is a small alpha helix, often referred to as helix 8 (H8). The crystallographic structure of the adenosine A 2A receptor reveals a ligand binding pocket distinct from that of other structurally determined GPCRs (i.e., the beta-2 adrenergic receptor and rhodopsin). [7]
MSX-3, MSX-4, and MSX-2 are xanthines and are derivatives of the non-selective adenosine receptor antagonist caffeine. [5] [6] MSX-2 has been extensively studied due to its high affinity and selectivity for the adenosine A 2A receptor, but use of MSX-2 itself has been limited by its poor water solubility.
Caffeine is an antagonist of all four adenosine receptor subtypes (A 1, A 2A, A 2B, and A 3), although with varying potencies. [5] [167] The affinity (K D) values of caffeine for the human adenosine receptors are 12 μM at A 1, 2.4 μM at A 2A, 13 μM at A 2B, and 80 μM at A 3. [167]
Caffeine's principal mode of action is as an antagonist of adenosine receptors in the brain. [ 12 ] Methylxanthines (e.g. caffeine found in coffee, theophylline found in tea, or theobromine found in chocolate) have a purine structure and bind to some of the same receptors as adenosine. [ 13 ]
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 ...
A 1 receptors are implicated in sleep promotion by inhibiting wake-promoting cholinergic neurons in the basal forebrain. [6] A 1 receptors are also present in smooth muscle throughout the vascular system. [7] The adenosine A 1 receptor has been found to be ubiquitous throughout the entire body. [citation needed]
136 11541 Ensembl ENSG00000170425 ENSMUSG00000018500 UniProt P29275 Q60614 RefSeq (mRNA) NM_000676 NM_007413 RefSeq (protein) NP_000667 NP_031439 Location (UCSC) Chr 17: 15.95 – 15.98 Mb Chr 11: 62.14 – 62.16 Mb PubMed search Wikidata View/Edit Human View/Edit Mouse The adenosine A 2B receptor, also known as ADORA2B, is a G-protein coupled adenosine receptor, and also denotes the human ...