Jeffrey B. Rosen, Ph.D. - US grants

Cocaine is one of the most potent reinforcers known; both humans and animals will crave and expend much energy to acquire these drugs. However, one of the many negative consequences of repeated cocaine use in humans is the development of panic and anxiety following cocaine withdrawal. Thus, cocaine has pleasurable, reinforcing properties, as well as anxiety-inducing effects. Although dopamine is known to be an important mediator of cocaine, stress hormones, such as corticosteroids, are thought to play a critical but paradoxical role in both the reinforcing and anxiety-inducing effects of cocaine. The goal of this proposal is to investigate the role of corticosteroids in the long-lasting anxiolytic (pleasurable) and anxiogenic properties of cocaine in rats. A paradigm that measures both long-lasting anxiolytic and anxiogenic effects of prior repeated cocaine administration by a single behavioral response, the acoustic startle reflex, will be described. Depending on the experience, both pleasurable and fearful states can be measured by the acoustic startle response. Startle decreases in an environment where the rats have previously been positively reinforced, and conversely, is increased following fear conditioning. The paradigm will be used to test the hypothesis that corticosteroids are critical for both the anxiolytic and anxiogenic effects of repeated cocaine following withdrawal. Adrenalecomized rats will be given repeated administration of cocaine, and then following a withdrawal period, will be tested for increased in pleasure and fear by measuring amplitude of the startle reflex. Corticosterone will also be given in an attempt to reverse the effects of adrenalectomy. In addition, pharmacological inhibition of corticosterone production will also be evaluated. The results will indicate whether corticosteroids are necessary for both the pleasurable and anxiety-inducing effects of cocaine, or for only one of the effects. The study will have important implications for understanding the environmental and behavioral control over the pleasurable and anxiogenic properties of cocaine and whether stress hormones regulate both of these properties or regulate cocaine-related pleasure and anxiety differentially. The outcome of the experiments should have ramifications for understanding drug abuse and relapse, and development of treatment and prevention strategies.

DESCRIPTION (provided by applicant): This R21 exploratory grant application will study a largely neglected and poorly understood principle of the ontogeny of learning---acquisition vs. expression---that will likely yield new insights into the development and neural basis of hippocampus-dependent memory. Research on acquisition vs. expression of delay fear conditioning during ontogeny has yielded novel and unanticipated insights concerning how the amygdala and specific efferent pathways cooperate to generate learned fear. However, other developmental research with other types of learning indicates that acquisition occurs first and expression of this learning emerges later in development. To explore these two possibilities in the case of hippocampus-dependent learning, Drs. Mark Stanton and Jeff Rosen at the University of Delaware;and Dr. Pam Hunt at the College of William and Mary will use behavioral, molecular and neuropharmacological approaches to study acquisition vs. expression of trace fear conditioning in developing rats. In Aim 1, two studies in the Hunt laboratory will explore the role of acquisition vs. expression of learning in the ontogenetic emergence trace conditioning between postnatal day (PD) 23 and PD28 in the rat. In Aim 2, immediate-early-gene expression assays will be performed in the Rosen laboratory on the brains of rats tested behaviorally in Aim 1 to explore the role of developmental differences in neural activity and/or plasticity in hippocampus and amygdala in the ontogeny of trace fear conditioning. In Aim 3, two experiments in the Stanton laboratory will determine the contribution of NMDA- receptor-mediated neural plasticity in dorsal hippocampus to the ontogeny of acquisition vs. expression of visual trace conditioning in PD23-28 rats. This project is innovative because it will be the first to examine acquisition vs. expression of hippocampus-dependent learning during ontogeny using an integrated, multidisciplinary approach. If successful, it will yield novel and important insights that would be pursued more thoroughly in subsequent R01 applications. The project is also significant because it will advance the study of developmental disorders involving aberrant maturation of the hippocampus. For example, Dr. Hunt's laboratory has shown that trace fear conditioning is an especially sensitive outcome measure for studying adverse cognitive effects of developmental alcohol exposure. However, understanding of the neural mechanisms of these effects is hampered by a lack of information on brain-behavior relationships mediating trace conditioning during this period of development. This R21 project seeks to fill that gap. Finally, this project will establish a new multi-investigator collaboration that has strong potential to advance these and other important issues in the developmental neurobiology of learning. PUBLIC HEALTH RELEVANCE: The proposed project will impact public health by establishing innovative new approaches to better understand the ontogeny of hippocampus-dependent memory, and determining whether processes of acquisition vs. expression contribute to the relatively late emergence of trace fear conditioning. The proposed project will advance both basic animal research and clinical practice directed at a broad range of developmental neurobehavioral disorders involving abnormal maturation of the hippocampus. By elucidating the developmental timing of acquisition vs. expression of cognitive function, the proposed research could cause assessment of, and interventions for, impaired cognitive development to occur earlier in ontogeny (when information is acquired) than is typical of current practices (which wait until stages of development when information is expressed). Finally, this application will advance public health via its translational application to ongoing research on rodent models of Fetal Alcohol Spectrum Disorder (FASD). If successful, it will help this ongoing research identify the developmental and neural mechanisms through which alcohol impairs cognitive development and through which nutritional or experiential interventions improve behavioral outcome.

DESCRIPTION (provided by applicant): The proposal advances 1) an empirical shift to a new psychological target, background anxiety, for common symptoms of anxiety, depression, schizophrenia and autism disorders, and 2) oxytocin, a hormone which selectively diminishes background anxiety. Current theories of anxiety emphasize learning where enhanced fear conditioning, impairments in fear extinction, and the inability to control learned fear lead to anxiety problems. However, symptoms of hypervigilance and exaggerated responsivity to unpredictable threat are typically independent of the specific fear memories. Therefore, the present proposal focuses on background anxiety - a type of anxiety in threatening situations that is characterized by anxious apprehension, hypervigilance and exaggerated startle to unpredictable events, but is not directly related to learned fear. We have recently found that subcutaneously administered oxytocin, a hormone that is associated with social interaction, affiliation, stress and anxiety, reduces background anxiety without affecting learned fear in a fear-potentiated startle test in rats. Intracerebroventricular administration of oxytocin also selectively reduces background anxiety, but with a higher dose than is needed with subcutaneous delivery. Oxytocin also reduces exaggerated startle produced by social isolation demonstrating that oxytocin promotes social resiliency. The specific aims of the proposal are to investigate the generality of background anxiety and social isolation anxiety by testing oxytocin on several potentiated startle paradigms. The pharmacological selectivity of oxytocin and comparison of systemic vs. central administration will be examined by testing oxytocin agonists and antagonists on background anxiety. The potential therapeutic value of oxytocin administration will be explored by examining its long-term effects on background anxiety. Finally, the neural basis of oxytocin's reduction of background anxiety will be studied by measuring changes in mRNA expression in brain circuits related to fear and anxiety. The proposal has significance and innovation by providing evidence about oxytocin's unique antianxiety profile using experimentally rigorous fear-potentiated startle paradigms. The investigation of oxytocin as a novel antianxiety agent for a novel type of background anxiety should lead to new directions for anxiety research and therapeutics. PUBLIC HEALTH RELEVANCE: Debilitating anxious apprehension, hypervigilance, and exaggerated responsivity to threat are common to many anxiety disorders, depression, schizophrenia and autism, but are typically not helped by current antianxiety medications. Preclinical studies of exaggerated startle suggest that the hormone oxytocin has novel anti-anxiety properties specifically for these symptoms. The research on oxytocin's effects of reducing these symptoms should provide new therapeutic directions for antianxiety treatments.

The role of the administrative core will be to coordinate resources, expertise and programs at Delaware State University and the University of Delaware to establish the joint Center for Neuroscience Research and develop a group of investigators at each institution and make them competitive for external funding for their research. Given that the PI, all of the target investigators and most other faculty affiliated with the Center are women, the Delaware Center for Neuroscience Research will have a special focus on supporting and mentoring women scientists. The Administrative Core will be centered at Delaware State University with a subcore at the University of Delaware ensuring coordination of efforts across both institutions. The PI and Dr. Rosen will oversee a structured mentoring program that will support the scientific and academic maturation of a group of female target investigators through quality interactions with established scientists and developmental activities. The administrative core will also implement a pilot grant program that will support junior faculty and faculty establishing interdisciplinary collaborations that cross institutional boundaries. The pilot projects will support faculty as they collect preliminary data to support future grant proposals, and will encourage them to collaborate and pursue research in areas relevant to the Center's mission. The pilot project Pis who are junior faculty will take part in the same structured mentoring program as the target investigators, and will be in line to become target investigators themselves as our first group graduates to independent funding. To build a critical mass of neuroscience researchers at DSU to support the interdisciplinary Delaware Center for Neuroscience Research, three new faculty lines have been committed in three different departments, including Public & Allied Health, Biology and Psychology. The PI and other Center-affiliated investigators will play key roles in the recruitment process to ensure that the new faculty are outstanding scientists with research interests relevant to the Center mission. Once the new faculty are in place, they will become part of the Delaware Center for Neuroscience Research either as target investigators or Pis of pilot projects.

DESCRIPTION (provided by applicant): In recent years, contextual fear conditioning has become a prominent paradigm for studying normal and abnormal development of conjunctive/spatial information processing in rodent models. However, very little is known concerning the neural mechanisms that cause context conditioning to emerge during ontogeny. We propose to use the context pre-exposure facilitation effect (CPFE) for this purpose. The CPFE is a variant of contextual fear conditioning in which learning about the context, consolidation and retrieval of the context memory, associating the context memory with shock, and retrieval of the context-shock association occur during separate phases of the procedure, making them especially amenable to experimental manipulations that can reveal underlying mechanisms. A recent model of the CPFE suggests that these processes depend on interactions between temporal cortical regions, the hippocampus, and the amygdala [65].. New data from our lab demonstrates the prefrontal cortex is also involved in the CPFE. Furthermore, we have recently shown that the CPFE emerges between Postnatal Day (PD) 17 and PD 24 in the rat and that antagonism of hippocampal NMDA receptors during context preexposure eliminates the effect on PD24 [74]. The present proposal will extend this work by examining the role of immediate early gene (IEG) activation and prefrontal cortex-hippocampus-amygdala interactions in the ontogeny of the CPFE. We have found distinct patterns of expression of the immediate early gene, Egr1, in these brain regions during different phases of the CPFE in juvenile rats (see Significance). Aim 1 will determine whether changes in these patterns of Egr-1 expression are associated with the early ontogeny of the CPFE. Aim 2 will use antisense to Egr1 to test a causal role for activation of these IEGs in the ontogeny of the CPFE. Aim 3 will extend the findings from Aims 1 and 2 to explore mechanisms of impaired cognitive development in an animal model of Fetal Alcohol Spectrum Disorder (FASD). We have recently shown that the CPFE is unusually sensitive to various doses and developmental windows of alcohol exposure in our established rodent model of FASD [49, 50]. Aim 3 will test the hypothesis that impaired IEG expression in the prefrontal cortex, hippocampus and/or amygdala contributes to the severe disruptions of the CPFE produced by developmental alcohol exposure. Taken as a whole, the work in this proposal will advance understanding of the mechanisms of cognitive development in the rat and promote translational applications of this understanding to human developmental learning disorders found in FASD.