Age-related loss of mRNA encoding adenosine A2 receptor in the rat striatum

The distributions of adenosine A2 receptor mRNA and adenosine A2 binding sites were studied by in situ hybridization histochemistry and receptor autoradiography in young (3 months) and old (24 months) rat striatum and compared to that of enkephalin mRNA. In the old striatum, the levels of adenosine A2 receptor mRNA and adenosine A2 binding sites were reduced by 32% and 20%, respectively. This decrease is similar to the 24% decrease of enkephalin mRNA and to the previously reported 20% neuronal loss. This indicated that, in contrast to the dopamine D2 receptor, the reduction of adenosine A2 receptors in the rat striatum during aging is mainly due to the neuronal loss.