Alterations to Dendrite Morphology in Response to Antipsychotic Drug Treatment and Hypoglutamatergia

Schizophrenia is a prevalent neurological disorder characterized by disrupted neuronal circuitry. Antipsychotic drugs (APDs) are capable of ameliorating the symptoms of schizophrenia with varying efficacy. Clozapine, the "gold-standard" for antipsychotic drug treatment, has been shown by this lab to induce the outgrowth of mediodorsal thalamic (MDT) dendritic arbor in rodents, a brain region which has altered function and decreased regional volume in schizophrenic patients. These studies further explored the ability of APD treatment to restructure dendrite arbor and the mechanisms of clozapine's ability to elaborate MDT arbor. Additionally, glutamate hypofunction is thought to contribute to the schizophrenic disease state. Using a novel model of perinatal glutamate hypofunction, we examined the long-term effects on dendritic architecture of developmental glutamate signaling disruption. MDT dysfunction is hypothesized to contribute to cognitive symptoms of schizophrenia. Clozapine has increased efficacy in ameliorating these symptoms. To further understand clozapine's actions to remodel MDT dendritic architecture, we examined whether clozapine-induced morphological alterations are limited to the thalamus or if they also occur in additional regions associated with cognitive schizophrenic pathology, the hippocampus and striatum. We found that clozapine can induce dendritic remodeling in the hippocampus, but the not to the amplitude of remodeling seen in the thalamus, indicating that the MDT is uniquely altered by clozapine treatment and may be an important locus of clozapine's action. The mechanisms of clozapine's remodeling of MDT arbor, we examined changes to mRNA and miRNA expression and calcium dynamics in the MDT in response to APD treatment. Clozapine-treatment altered the expression of genes involved in cytoskeletal remodeling, external membrane receptors, and calcium dynamics, as well as increased the rate of calcium influx into thalamic neurons. Disruption to glutamate signaling has been hypothesized to contribute to schizophrenic pathology. Disruption to perinatal vesicular glutamate packaging along the corticolimbic axis has long term effects for neuronal morphology and function. Interestingly, we find that disruption along the corticolimbic axis also has downstream effects on MDT dendritic architecture. These studies show that the MDT is an important locus of action for clozapine and is capable of remodeling dendritic architecture in response to afferent circuitry dysfunction