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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 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]
It is a xanthine and a derivative of the non-selective adenosine receptor antagonist caffeine. [ 1 ] [ 2 ] The affinities (K i ) of MSX-2 for the human adenosine receptors are 5.38 to 14.5 nM for the adenosine A 2A receptor, 2,500 nM for the adenosine A 1 receptor (172- to 465-fold lower than for the A 2A receptor), and >10,000 nM for the ...
Studies indicate that, similar to caffeine, simultaneous antagonism of adenosine receptors [9] is responsible for paraxanthine's stimulatory effects. Paraxanthine adenosine receptor binding affinity (21 μM for A1, 32 μM for A2 A, 4.5 μM for A2 B, and >100 for μM for A3) is similar or slightly stronger than caffeine, but weaker than theophylline.
Caffeine exerts its psychoactive and sympathomimetic effects by acting as an antagonist at adenosine receptors. [9] d9-Caffeine was assessed for human adenosine receptor antagonism at the four receptor subtypes: A1, A2A, A2B, and A3, and found to have similar adenosine receptor affinity as caffeine. [3]
In the human body, caffeine blocks adenosine receptors A 1 and A 2A. [5] Adenosine is a by-product of cellular activity: the stimulation of adenosine receptors produces sedation and a desire for sleep. Caffeine's ability to block these receptors means the levels of the body's natural stimulants, dopamine and norepinephrine, continue at higher ...
Caffeine acts as an antagonist of adenosine A 1 and A 2A receptors. Adenosine is a normal neuromodulator that activates adenosine g-protein coupled receptors. The actions of A 1 and A 2A receptors oppose each other but are both inhibited by caffeine due to its function as an antagonist. [8]