Ns-Subatituted 9-methyladenines are potent antagonists of the activation of AI adenosine receptors. The present study asseased the effect of N8 and N-9 Substituents on the binding of adenines to the Al and & receptors, respectively, of rat brain cortex and striatum and also on the antagonism of the Az receptor mediated stimulation of the adenylate cyclase of PC12 cells by N-ethyladenosine-5'-uronamide. The potency ranking of 9-substituted adenines ...