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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]
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 ...
Mast says that “only sleep clears that adenosine. Caffeine does not give you energy, just delays fatigue for a little while longer.” In other words, that 2 p.m. cup of coffee is just delaying ...
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 ]
It blocks tiredness-causing adenosine from receptors in the brain. Patricca explains the optimum amount of caffeine is 3-6 milligrams per kilogram of body weight.
Experts say that the window of 9:30 a.m. to 11 a.m. may be the best time to consume coffee.
Compared with caffeine, theobromine is weaker in both its inhibition of cyclic nucleotide phosphodiesterases and its antagonism of adenosine receptors. [4] [32] The potential phosphodiesterase inhibitory effect of theobromine is seen only at amounts much higher than what people normally would consume in a typical diet including chocolate. [33]