Beth Levant - US grants

DESCRIPTION (Adapted from applicant's abstract): The D3 dopamine receptor is a novel receptor which has been implicated as a potential therapeutic target in the treatment of schizophrenia.This proposal addresses the issue of whether the D3 receptor mediates any of the therapeutic and/or side-effects of antipsychotic drugs. The hypothesis is that D3 receptors in limbic brain regions may mediate the therapeutic effects of antipsychotic drugs, while cerebellar D3 receptors may mediate certain neurological side-effects. Molecular, biochemical, pharmacological, anatomical, and behavioral approaches will be used to address the specific aims: (1) to determine how D3 receptors are regulated by tonic dopaminergic activity. The effects of unilateral and bilateral 6-OHDA lesions of the major dopamine projections on the density of D3 receptors and mRNA indiscrete brain regions will be examined using receptor autoradiography, receptor binding, and in situ hybridization. (2) to determine how D3 receptors are regulated by dopamine agonists and antagonists using receptor autoradiography, receptor binding, and in situ hybridization. (3) to determine D3 receptor occupation by antipsychotic drugs in vivo using receptor autoradiography. (4) to determine the effects of D3 receptor stimulation or blockade on neuronal activity in specific brain regions by assessment of (a) Fos expression and (b) cerebral glucose utilization. (5) to determine whether cerebellar D3 receptors have dopaminergic innervation and, if so, the source. Autoradiographic methods, measurement of catecholamines by HPLC-EC, and retrograde tracers will be used. (6) to determine whether cerebellar dopamine receptors are present in humans and other mammalian species using receptor autoradiography and in situ hybridization. (7) to determine the behavioral effects of microinjection of dopamine agonists and antagonists into cerebellar lobule 10. These studies will provide significant information regarding the functional role of D3 receptor, its potential involvement in the effects of antipsychotic drugs, and its suitability as a therapeutic target.

[unreadable] DESCRIPTION (provided by applicant): A growing body of evidence suggests that inadequate incorporation of docosahexaenoic acid (DHA) in brain during development affects the CNS dopamine systems and, when combined with appropriate genetic and/or other epigenetic factors, contribute to the risk of developing ADHD or to the severity of the disease. This proposal addresses the HYPOTHESIS that low brain DHA levels during early development alter dopaminergic function producing hyperactivity and attentional deficits similar to the symptoms of ADHD. The OBJECTIVE of this study is to assess the behavioral and neurochemical effects of clinically-relevant variation in brain DHA content during early development. The Specific Aims will use a rat model to determine: [unreadable] [unreadable] 1. The effects of low brain DHA content during early development on activity and attentional processes in the developing rat. A force-plate actometer will be used to measure simultaneously assess activity and attentional processes in rats raised from conception on diets designed to modulate brain DHA content. [unreadable] [unreadable] 2. The effects of methylphenidate on hyperactivity and attentional processes in juvenile rats with low brain DHA content during early development. Dose-response effects of this drug used in the treatment of ADHD will be determined using the force-plate actometer. [unreadable] [unreadable] 3. The effects of low brain DHA content during early development on dopaminergic neurochemistry in juvenile rats. Dopamine content and turnover and the density of dopamine receptors and transporters will be assessed in specific brain regions. [unreadable] [unreadable] 4. The critical developmental period(s) when sufficient brain DHA content is essential for normal development of the dopamine systems. Treatment with DHA will be initiated at various time points between birth and weaning to determine when neuroplasticity is present. [unreadable] [unreadable] These experiments will show the relationship between brain DHA content and dopaminergic functioning and behavioral indices of hyperactivity and attentional processes. These findings will provide timely and important insights into mechanisms of brain development and perinatal nutrition and provide insights into the etiology of ADHD in humans. Such insights may identify a means by which certain risk factors for ADHD may be reduced or eliminated or the severity of the disease may be reduced through appropriate pre- and postnatal nutrition. [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Alterations in brain long-chain polyunsaturated fatty acid (LC-PUFA) composition, particularly decreased docosahexaenoic acid (DHA), are implicated as a contributing factor in depression and psychosis. Our preliminary data indicates that pregnancy and lactation can deplete the maternal brain of DHA. Accordingly, these studies are designed to test the HYPOTHESIS that depletion of maternal brain DHA during pregnancy and lactation contributes to postpartum mental illness. The Specific Aims will use a rat model to: 1. Determine the effects of pregnancy and lactation on levels of maternal brain DHA and other LC-PUFA. Manipulation of dietary fatty acid content will be used to alter maternal brain DHA levels. LC-PUFA will be assessed in four brain regions associated with depression and psychosis, as well as in erythrocytes. These studies will establish a rodent model with which to study the effects of depleted brain DHA levels following pregnancy and lactation on neurochemical parameters associated with depression and psychosis in humans. 2. Determine the effects of reduced brain DHA in the postpartum period on maternal hypothalamic-pituitary-adrenal (HPA) axis activity and regulation. Regulation of the HPA axis will be assessed using a modification of the dexamethasone suppression test. The affinity and density of cerebral cortical corticotrophin releasing factor1 (CRF1) receptors will also be quantified. 3. Determine the effects of reduced brain DHA in the postpartum period on monoamine neurochemistry. The concentrations of serotonin, norepinephrine, and dopamine (and their respective metabolites) will be measured in brain regions relevant to depression or psychosis. The affinity and density of receptors most strongly implicated in depression or psychosis (5-HT1A, 5-TH2A, beta, D2, and D3) will also be quantified. 4. Determine the effects of reduced brain DHA in the postpartum period on expression of brain-derived neurotrophic factor (BDNF) in hippocampus. Hippocampal expression of the BDNF gene, which is decreased in animal models of depression, will be measured by RNAse protectionassay. These experiments will determine whether reproductive activity and the resulting alterations in maternal brain LC-PUFA content are likely to contribute to postpartum mental illness in women. Findings will point to causes of postpartum mental illness and thus the identification of women at risk and the elimination of risk factors. These findings will also suggest novel treatments for such illnesses when they occur.

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) is a major public health concern with consequences including long-term loss of function or death. Accordingly, there is a significant need for improved treatments and other means for improving outcomes in TBI, especially in small children who are particularly likely to suffer such an injury. Mechanisms of TBI include inflammation, blood-brain barrier disruption, and neuronal death. The n-3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA) has anti- inflammatory and anti-apoptotic activities. Diet n-3 PUFA content influences the levels of DHA that are incorporated into tissues, including the brain, where DHA continues to accumulate into at least the second year of life. The American diet is notably low in n-3 PUFAs;thus, Americans are at particular risk of having low tissue DHA levels. Acute administration of DHA improves outcomes in animal models of spinal cord injury and stroke. However, it is not known whether DHA has beneficial effects in TBI or whether diet n-3 content, and thus tissue DHA levels, influence TBI outcomes. The PIs'overall goal is to improve outcomes of TBI in young children. The objective of this application is to determine the effects of diet n-3 PUFA content, acute DHA treatment, and their interaction on outcomes in a rat model of TBI in toddlers. The PIs hypothesize that low diet n-3 PUFA content will be associated with poorer TBI outcomes, that acute DHA treatment after TBI will improve outcomes, and that acute DHA treatment and diet n-3 PUFA content will interact to affect outcomes in TBI. An innovative approach, integrating nutritional and neurobiological methods will be used to pursue the following Specific Aims: 1) Determine the effects of diet n-3 PUFA content on outcomes of TBI and 2) Determine the effects of acute DHA administration on outcomes of TBI in rats fed diets varying in n-3 PUFA content. Disruption of the blood-brain barrier, which is central to the pathological sequelae after TBI, and functional motor deficits and recovery, will be assessed. Expected outcomes include readily translatable findings on the potential utility of DHA treatment and/or increased dietary n-3 PUFA content in improving outcomes in pediatric TBI, and greater understanding of the role of DHA in the central nervous system with respect to inflammation, maintenance of the blood-brain barrier, and neuronal survival/death. Such findings may be anticipated to form a basis for future clinical studies that lead to novel therapeutic and/or preventative interventions to improve outcomes in pediatric TBI. These data will also form a platform from which to launch expanded basic studies of mechanisms underlying the beneficial effects of DHA in TBI, which may be anticipated to lead to the identification of novel targets for therapeutic intervention in TBI. Relevance: Traumatic brain injury affects at least 1.4 million Americans each year and is a significant cause of death and long-term disability. Children 0-4 years old are at the highest risk. This study seeks to identify means to improve outcomes of TBI in young children.

DESCRIPTION (provided by applicant): Individuals with fewer nigrostriatal dopamine neurons appear to have increased vulnerability to insults and neuropathological processes that lead to Parkinson's disease. We have shown that young adult rats raised from conception on a diet low in n-3 (omega-3) polyunsaturated fatty acids (PUFAs) have decreased brain levels of the n-3 PUFA docosahexaenoic acid (DHA) and decreased numbers of nigrostriatal dopamine neurons. The objective of this application is to identify mechanisms by which an n-3 PUFA-deficient diet leads to decreased numbers of nigrostriatal dopamine neurons, and if this decrease in dopaminergic cell number leads to increased sensitivity to dopaminergic neurotoxins. The hypothesis is that decreased brain DHA content leads to decreased survival of dopamine neurons under normal and pathological conditions. The Specific Aims are to identify candidate mechanisms by which low dietary n-3 PUFA content results in decreased numbers of nigrostriatal dopamine neurons and determine the effects of low dietary n-3 PUFA content on neurotoxic lesion of nigrostriatal dopamine neurons. Expected outcomes from these studies include novel means for preventing and/or slowing progression of Parkinson's disease, as well as increased understanding of the role of phospholipid long chain PUFA composition in neuronal function. Findings may also clarify the underlying pathology of Parkinson's disease, and form a basis for future clinical studies. PUBLIC HEALTH RELEVANCE: Parkinson's disease is a debilitating progressive neurodegenerative disorder affecting 0.1-0.2% of the general population and 2% of people over 65 years of age. The objective of this application is to identify potential factors contributing to the development of Parkinson's disease using a rat model.