Allosteric potentiator at the adenosine A1 receptor; acts via agonist-dependent and -independent mechanisms. Enhances agonist affinity for, and increased t½ of dissociation from, the receptor. Also inhibits basal and forskolin-stimulated adenylyl cyclase (AC) activity in A1 receptors expressed in CHO cells, possibly via direct potentiation of constitutive receptor activity or by direct inhibition of AC. Active in vivo.