Adenosine is a chemical in your brain and body that belongs to a class of substances called neurotransmitters. These substances support basic nervous system communication by carrying "messages" across the gaps between individual nerve cells. Adenosine transmission appears to regulate some of the most basic functions of your brain's sleep cycle, and differences in adenosine levels between individuals seem to play a role in relative quality of sleep.
Your body makes adenosine from a combination of a nitrogen-based substance called adenine and a sugar called ribose. In addition to its designation as a neurotransmitter, adenosine belongs to a class of chemicals called xanthines. Every cell in your body contains some adenosine inside its DNA and RNA; it is also found in the energy source adenosine triphosphate, or ATP, and related chemicals called adenosine diphosphate, or ADP, and adenosine monophosphate, or AMP. In addition, adenosine acts as a natural painkiller, helps widen your blood vessels and helps steady your heartbeat.
Although your body rests during sleep, your brain remains highly active. The phases of sleep during any given night include stage 1 sleep, during which you can typically awaken easily; stage 2 sleep, during which your brain waves start to slow and your eye movements stop; stage 3 sleep, during which very slow brain waves start to appear, stage 4 sleep, during which very slow brain waves predominate; and the dreaming state, or REM sleep. This last stage is marked by temporary limb paralysis, rapid eye jerking and rapid, shallow erratic breathing.
Adenosine's Effects on Sleep
Adenosine appears to accumulate in your bloodstream when you're awake and eventually makes you drowsy, the National Institute of Neurological Diseases and Stroke explains. Inside your brain, your adenosine levels exert a major influence on the regulation of non-REM sleep, according to a 2008 study published in "Biochemical Pharmacology." This regulating effect occurs when an enzyme called adenosine deaminase breaks down, or metabolizes, adenosine molecules. The rate of this metabolism has an effect on the intensity and duration of sleep when slow brain waves are present. Metabolism also reduces your brain's adenosine supplies, and your adenosine levels drop as sleep continues.
Conclusions and Considerations
Your brain's specific rate of adenosine metabolism appears to determine the quality of your deep sleep, the authors of the study in "Biochemical Pharmacology" report. In addition, adenosine metabolism in your brain appears to help determine your vulnerability to the effects of sleep deprivation. However, the study authors note the need for further research to confirm their conclusions. Like adenosine, the caffeine found in coffee, tea and other beverages is a xanthine chemical. When you drink caffeine, it achieves its stimulating effects by blocking your brain's adenosine processing. Consult your doctor for more information on adenosine and its effects on your sleep patterns.