Adenosine in the mammalian heart: nothing to get excited about

Until quite recently, the cardiodepressant actions of adenosine were widely accepted. A nucleoside that produces negative chronotropic and ionotropic effects, adenosine, has been used clinically as the drug of choice for terminating supraventricular (atrioventricular node) tachycardia and is likely to play an important part in regulating arrhythmogenic activity as an endogenous antiarrhythmic metabolite. Despite this, recent experimental data, particularly resulting from in vitro studies using animal models, have shown a paradoxical excitable action of adenosine in the heart. In this article, Amir Pelleg and Steven Kutalek present the reasons why they continue to believe that any excitatory actions of adenosine in the heart are clinically irrelevant.