Striatal restricted adenosine A2 receptor (RDC8) is expressed by enkephalin but not by substance P neurons: an in situ hybridization histochemistry study.

RDC8 has been recently cloned and characterized as an adenosine A2 receptor. This receptor is expressed exclusively by medium-sized neurons of the striatum as demonstrated by in situ hybridization. We have now studied the relationship of this receptor with three major components of the rat caudate-putamen: enkephalin, substance P, and choline acetyltransferase. Our results demonstrate that the adenosine A2 receptor is expressed exclusively by the enkephalinergic striatal subpopulation but not by the substance P-containing or cholinergic neurons.