Adenosine and schizophrenia: mechanisms and therapies Project Summary: Schizophrenia (SZ) is a debilitating mental illness with tremendous human, social and financial costs to society. Unfortunately, existing treatments are unsatisfactory and current development remains stagnant due to poor understanding of the biological bases of the disease. Two perspectives have emphasized disturbances in two neurochemical messengers in the brain -dopamine and glutamate, in relation to disparate SZ- symptoms. This proposal will examine a third messenger -adenosine (ADO), as a potential link uniting the dopamine and glutamate hypotheses of SZ. ADO can regulate both dopamine and glutamate neurotransmission via receptors with opposing actions (A1 vs. A2A adenosine receptors). ADO is therefore uniquely positioned as an upstream coordinator/regulator between these two neurotransmitter systems. Hence, ADO-based treatment may be an attractive alternative with dual corrective actions on the glutamate and dopamine systems, thereby achieving effective control over selected SZ symptoms. Our central hypothesis is that subtle disturbances in adenosinergic neuromodulation can give rise to selected behavioral endophenotypes implicated in SZ;thus corresponding corrective interventions targeting at the ADO system should confer therapeutic potential against such SZ endophenotypes, and thereby validate our hypothesis. Our hypothesis will be tested by three specific aims. First, we will characterize the emergence of selected SZ-related endophenotypes as well as their opposing phenotypes in transgenic mice with either over- or under- expression of brain ADO achieved by genetic manipulation of adenosine kinase. Second, we aim to identify the molecular mechanisms of adenosine-based modulation of dopaminergic and glutamatergic neurotransmission. This will be achieved by behavioral and biochemical examination of A1R and A2AR knockout mice. Third, we aim to dissect the brain regions in which ADO-dopamine interactions and ADO-glutamate interactions contribute to the regulation of specific SZ-related endophenotypes. To achieve this, ADO will locally be modified by transplantation of ADO-secreting stem cells and by focal infusion of drugs acting on ADO-receptors. The expected outcomes of this project include: (i) the biological validation of a novel neurochemical theory of SZ, and (ii) the feasibility-test of a novel ADO-based strategy to produce behavioral adjustment with therapeutic potential.
Schizophrenia is a devastating mental disorder to the individual and society alike, yet the efficacy of current drug treatment remains poor, and the development of novel drugs is limited to either blocking dopamine or enhancing glutamate neurotransmission. This proposal will examine a novel drug target for schizophrenia-therapy -adenosine: Given adenosine's unique position to interact in parallel with dopamine and glutamate neurotransmission, adenosine-modulating drugs are hypothesized to confer therapeutic potential against multiple SZ symptoms.
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