Mapping adenosine A1 receptors in the cat brain by positron emission tomography with [11C] MPDX.

We evaluated the potential of[11C]MPDX as a radioligand for mapping adenosine A1 receptors in comparison with previously proposed[11C]KF15372 in cat brain by PET, Two tracers showed the same brain distribution. Brain uptake of[11C]MPDX (Ki=4.2nM)was much higher and washed out faster than that of[11C]KF15372 (Ki=3.0nM),and was blocked by carrier-loading or displaced with an A1 antagonist. The regional A1 receptor distribution evaluated with kinetic analysis is consistent with that previously measured in vitro.[11C]MPDX PET has a potential for mapping adenosine A1 receptors in brain