Ontogeny of gene expression of adenosine A2 receptor in the striatum: Early localization in the patch compartment

Abstract

The ontogeny of adenosine A₂ receptor mRNA and adenosine A₂, binding sites distributions was studied by in situ hybridization histochemistry and receptor autoradiography in pre‐ and post‐natal rat striatum, postnatal dog striatum, and a human fetus striatum and compared to that of dopamine D1 and μ opiate receptors. The early postnatal striatum demonstrated heterogeneous distributions of adenosine A₂ receptor mRNA and adenosine A₂ binding sites with patches of dense labeling corresponding to dopamine D1 and μ opiate receptors enriched zones. This patchy pattern evolved to the homogeneous distribution observed in the adult. The higher intensity of adenosine A₂ receptor mRNA enriched patches correspond at the microscopical level to a higher density of labeled neurons in the patches areas and also to a higher level expression per labeled patches neuron than in the matrix ones. This demonstrates for the first time that differences in patch/matrix receptor density is at least partly linked to different levels of receptor gene expression.