2-Chloro-N6-cyclopentyladenosine (CCPA) may be used as an A1 adenosine receptor agonist with high selectivity. CCPA is often used with other adenosine receptor agonists and antagonist to resolve A(1), A(2A) and A(3) receptor functions. These include DPCPX (A(1) receptor antagonist), 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-α][1,3,5]triazin-5-ylamino]ethyl)phenol (A(2A) receptor antagonist), and 4-[2-[[6-amino-9-(N-ethyl-β-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (A(2A) receptor agonist), and Cl-IB-MECA, (A(3)) receptor agonist).