Ligand Recognition Sites on P2XReceptors Studied by Quantitative Autoradiography of [3H]α,β-Methylene-ATP Binding in Rat Brain

The specificity of α,β-methylene-ATP for P2Xreceptor binding sites in the CNS has been examined by testing the effects of several ATP analogues and other ATP-related substances on the binding of 10 nM [3H]α,β-methylene-ATP to 20 μm thick sections of fresh-frozen rat brain. The labelling of the putative P2Xreceptor binding sites by [3H]α,β-methylene-ATP was evaluated by quantitative densitometry. [3H]α,β-Methylene-ATP binding was strongly inhibited by two close ATP analogues, 3′-O-(trinitrophenyl)-adenosine-5′-triphosphate and β,γ-imido-ATP (IC502-5 μM). β,γ-Methylene-ATP was, however, less potent (