The adenosine receptors are a class of G-protein coupled receptors with adenosine as endogenous ligand. In cell biology, G-protein-coupled receptors, also known as GPCR, seven transmembrane receptors, heptahelical receptors, or 7TM receptors, are a class of transmembrane receptors. ... The chemical structure of adenosine Adenosine is a nucleoside comprised of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. ... In an economic model, an endogenous change is one that comes from inside the model and is explained by the model itself. ... It has been suggested that this article or section be merged with Ligand (biochemistry). ...

A₁ adenosine receptor

A_2A adenosine receptor

The A1 and A2a receptors of endogenous adenosine are believed to play a role in regulating myocardial oxygen consumption and coronary blood flow[1]. Stimulation of the A1 receptor has a myocardial depressant effect by decreasing the conduction of electrical impulses and suppressing pacemaker cell function, resulting in a decrease in heart rate. This makes adenosine a useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This effect on the A1 receptor also explains why there is a brief moment of cardiac standstill when adenosine is administered as a rapid IV push during cardiac resuscitation. The rapid infusion causes a momentary myocardial stunning effect. A cardiac arrhythmia, also called cardiac dysrhythmia, is a disturbance in the regular rhythm of the heartbeat. ...

In comparison, the A2a receptor is responsible for regulating myocardial blood flow by vasodilating the coronary arteries, which increases blood flow to the myocardium, but may lead to hypotension. In normal physiological states, both of these receptors serve as protective mechanisms. However, in altered cardiac function, such as hypoperfusion caused by hypotension, heart attack or cardiac arrest caused by nonperfusing bradycardias, adenosine has a negative effect on physiological functioning by preventing necessary compensatory increases in heart rate and blood pressure that attempt to maintain cerebral perfusion. The coronary circulation consists of the blood vessels that supply blood to, and remove blood from, the heart. ... Myocardium is the muscular tissue of the heart. ... In medicine, shock (hypoperfusion) is a life-threatening medical emergency characterized by inability of the body to supply enough oxygen to meet tissue requirements. ... In physiology and medicine, hypotension refers to an abnormally low blood pressure. ...

Recent research on adenosine receptor function, and adenosine receptor antagonists such as theophylline has lead to several randomized controlled trials using these receptor antagonists to treat bradyasystolic arrest[1-8]. The primary researchers, TJ Mader et al at Tuffs University School of Medicine, have reported some promising results. Antagonists In medicine and biology, a receptor antagonist is a substance that inhibits the normal physiological function of a receptor. ... Theophylline is a methylxanthine drug and is used in therapy for respiratory diseases, under a variety of brand names. ...

A_2B adenosine receptor

A₃ adenosine receptor

It has been shown in studies to inhibit some specific signal pathways of adenosine. It allows for the inhibition of growth in human melanoma cells.

References / Resources for more information

1. Mader TJ, Bertolet BD, Ornato JP, Gutterman JM. Aminophylline in the treatment of atropine resistant bradyasystole. Resuscitation. 2000;47:105-112.

2. Burton JH, Mass M, Menegazzi JJ, Yealy DM. Aminophylline as an adjunct to standard advanced cardiac life support in prolongued cardiac arrest. Ann Emerg Med. 1997;30:154-160.

3. Khoury MY, Moukarbel GV, Obeid MY, Alam SE. Effects of aminophylline on conplete atrioventricular black with ventricular asystole following blunt chest trauma. Injury, Int J care Injured. 2001;32:335-338. [case report].

4. Mader TJ, Smithline HA, Durkin L, Scriver G. A randominzed controlled trial of intravenous aminophylline for atropine resistant out-of-hospital asystolic cardiac arrest. Acad Emerg Med. 2003;10:192-197.

5. Mader TJ, Smithline Ha, Gibson P. Aminophylline in undifferentiated out-of-hospital asytolic cardiac arrest. Resuscitation. 1999;41:39-45.

6. Mader TJ, Gibson P. Adenosine receptor antagonism in refractory asystolic cardiac arrest: results of a human pilot study. Resuscitation. 1997;35:3-7.

7. Perouansky M, Shamir M, Hershkowitz E, Donchin Y. Successful resuscitation using aminophylline in refractory cardiac arrest with asystole. Resuscitation. 1998;38:39-41. [case reports].

8. Viskin S, Belhassen B, Roth, A, et al. Aminophylline for bradysystolic cardiac arrest refractory to atropine and epinephrine. Ann Intern Med. 1993;118:279-281.

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