Immunocytochemistry Studies of Basal Ganglia Adenosine A2A Receptors in Rat and Human Tissue

Abstract

The present studies describe the development of immuno-histochemical methods for characterizing the presence of adenosine A2A receptors on basal ganglia neurons in humans and rats. Antigen retrieval methods were incorporated to decrease the expression of nonspecific tissue binding and to amplify antigen sensitivity. Morphology of the tissue sec-tions was not disturbed by antigen retrieval, and the quality of staining was enhanced substantially. Conditions were optimized for visualizing adenosine A2A receptor antibody in sections of rat and human basal ganglia, and comparing the distributions of A2A receptor labeling across multiple striatal cell populations. The retrograde tracer cholera toxin B was injected into different pallidal regions to visualize projec-tions from multiple striatal subregions, and to determine if the cholera toxin B-labeled striatal neurons also contained adenosine A2A receptor immunoreactivity. Apparent double-labeled neurons were observed in both nucleus accumbens and neostriatum. Thus, these immunohistochemical methods provided evidence that striatal neurons that topographically project to distinct pallidal areas also contain adenosine A2A receptor immunoreactivity. Development of immunohis-tochemical methods can contribute to our understanding of the role that basal ganglia receptors play in modulating the forebrain circuitry involved in motor functions and effort-related motivational processes.