A1 is a receptor for adenosine. It is demonstrated that the A1 receptor is ubiquitous throughout the entire body. Activation of A1 elicits an inhibition of adenylate cyclase and therefore a decrease in the cAMP concentration. A1 receptors are implicated in sleep promotion by inhibiting wake promoting cholinergic neurons in the basal forebrain. Adenosine antagonists are widely used in neonatal medicine.