To examine the mechanisms underlying the adenosine A2a/dopamine D2 and the adenosine A1/dopamine D1 receptor interactions at the cellular level, using fibroblast cell lines cotransfected with different combinations of cDNAs of adenosine A1 and A2a receptors and dopamine D1 and D2 receptors, as well as striatal cell cultures.
To characterize the changes in striatal A2a/D2 and A1/D1 receptor interactions occurring in a rat model of Parkinson' s disease, to evaluate the possible role of adenosine antagonists as a therapeutic strategy for Parkinson' s disease.
A large number of studies have demonstrated that adenosine can interact with dopaminergic neurotransmission in the basal ganglia. The working hypothesis of the present project states that the interplay between adenosine and dopamine in the basal ganglia is mediated through specific interactions between adenosine and dopamine receptor subtypes, mainly between adenosine A2a and dopamine D2 receptors and between adenosine A1 and dopamine D1 receptors.
The first objective is to determine the basic mechanisms of the A2a/D2 and the A1/D1 receptor interactions at the cellular level using fibroblast cell lines stably cotransfected with different combinations of A2a, A1, D2 and D1 human receptor cDNAs and primary striatal cultures. These receptor interactions will be studied at the receptor level (radioligand binding experiments), second messenger level (adenylate cyclase activation experiments) and functional level (intracellular calcium influx experiments). A2a/D2 and A1/D1 receptor interactions will also be studied in human basal ganglia by using quantitative receptor autoradiography.
The second objective is to characterize the changes in striatal A2a/D2 and A1/D1 receptor interactions taking place in an animal model of Parkinson' s disease (unilateral 6-OH-dopamine lesioned rats) and to evaluate the role of adenosine antagonists as a therapeutic strategy for this disease. In that model we will analyze: First, how A1 and A2a agonists and antagonists modulate D2- and D1-induced behavioural effects in rats with and without previous chronic treatment with adenosine antagonists. Second, how A1 and A2a agonists and antagonists modify the changes in the transcription of proto-oncogenes and peptides induced by the D2 and D1 agonists. Third, the ability of adenosine A2a and A1 agonists to modulate the binding characteristics of the D2 and D1 receptors in the different parts of the basal ganglia. Finally, we will study how the A2a and A1 receptors modulate the D2 and D1 ionic currents in acutely dissociated striatal neurons. This second objective, therefore, focuses on the analysis of the A2a/D2 and A1/D1 receptor interactions in an experimental model of Parkinson' s disease, with the aim of developing of adenosine antagonists for the treatment of that brain disorder (by enhancing dopamine receptor function in the striatum).
Funding SchemeCSC - Cost-sharing contracts