Neural ECM in addiction, schizophrenia, and mood disorder

The extracellular matrix (ECM) has a prominent role in brain development, maturation of neural circuits, and adult neuroplasticity. This multifactorial role of the ECM suggests that processes that affect composition or turnover of ECM in the brain could lead to altered brain function, possibly underlying conditions of impaired mental health, such as neuropsychiatric or neurodegenerative disease. In support of this, in the last two decades, clinical and preclinical research provided evidence of correlations and to some degree causal links, between aberrant ECM function and neuropsychiatric disorders, the most prominent being addiction and schizophrenia. Based on these initial observations of involvement of different classes of ECM molecules (laminin, reelin, and their integrin receptors, as well as tenascins and chondroitin sulfate proteoglycans), ECM targets have been suggested as a novel entry point in the treatment of neuropsychiatric disorders. Hence, understanding how ECM molecules contribute to proper neuronal functioning and how this is dysregulated in conditions of mental illness is of pivotal importance. In this chapter, we will review available literature that implicates the different classes of brain ECM molecules in psychiatric disorders, with a primary focus on addiction (opiates, psychostimulants, and alcohol), and we will compare these ECM adaptations with those implicated in schizophrenia and mood disorders.