Adenosine is a neuromodulator widely distributed throughout thebody. Since it is continuously synthesized, it can be concluded thatthere is a basal adenosinergic tonus, which has inhibitory effects ingeneral. All of the three adenosine receptors are G-protein coupled.While A1and A3receptor subtypes inhibit adenylate cyclase, A2subtypes activates it. A1and A2Areceptor subtypes, which bindadenosine with high affinity, are responsible for the basaladenosinergic tonus in physiological conditions. The most widelydistributed subtype, A1, is concentrated particularly in cerebral cortex,cerebellum and hippocampus. Adenosine has intense interactionswith other receptor systems. There are antagonistic interactionsbetween A1 dopamine D1and between A2and D2receptors.Adenosine is implicated in physiological processes such as initiationand maintenance of sleep, modulation of arousal, and control ofcerebral blood flow in response to energy demand of the brain.Adenosine is also implicated in cell-protection in pathologicalconditions like hypoxia and ischemia. Adenosine might be importantin the pathophysiology of anxiety, epilepsy, depression,schizophrenia, Parkinson’s disease, and addiction. The currentliterature about the central adenosinergic system is reviewe
