Adenosine uptake sites in rat brain: identification using [3H]nitrobenzylthioinosine and co-localization with adenosine deaminase.

The binding characteristics of [3H]nitrobenzylthioinosine ([3H]NBI) to rat brain membrane preparations was examined, and the autoradiographic distribution of this ligand in brain sections was compared with the immunohistochemical localization of adenosine deaminase (ADA). It was found that [3H]NBI labels sites for which adenosine has far higher affinity than do other nucleosides, that these sites are heterogeneously distributed and that there is an exact correspondence between areas containing [3H]NBI sites and ADA-immunoreactive neurons. Our results indicate that [3H]NBI and ADA are potential markers for revealing anatomical sites at which actions of adenosine may be expressed.