Irwin Lucki - US grants

DESCRIPTION: (Adapted From The Applicant's Abstract) Effects on serotonergic neurotransmission underlie the clinical therapeutic effects of serotonin reuptake inhibitors (SSRIs), the class of drugs most frequently prescribed for the treatment of depression. Nevertheless, very little information is available about how SSRIs produce their behavioral effects. Research supported by this project examines the pharmacological and physiological basis underlying the antidepressant behavioral effects of SSRIs and other putative serotonergic antidepressants. The behavioral effects of antidepressant drugs are studied using the rat forced swimming test, a behavioral test that successfully predicts the clinical effects of antidepressant drugs. A version of the rat forced swimming test developed by this laboratory is used that measures the core response of immobility and component active behaviors and distinguishes antidepressants pharmacologically selective for serotonergic and catecholamine systems. The neurochemical effects of antidepressants and forced swimming are studied using in vivo microdialysis, which permits the release of 5-HT to be measured in discrete brain regions in awake unrestrained animals. The proposed research program will continue to investigate the neural substrates underlying the antidepressant behavioral effects of SSRIs. The first specific aim will characterize and distinguish the role of serotonin and catecholamine systems in the behavioral effects of an extended series of antidepressant drugs in the forced swimming test. Studies will also identify 5-HT receptor subtypes that are involved in the behavioral effects of SSRIs and that are likely to produce antidepressant effects. The second specific aim will employ the neurochemical depletion of 5-HT to establish the role of intact serotonergic neurons in the behavioral effects of different types of antidepressant drugs. Studies involving localized depletion of 5-HT will identify the brain regions likely to be associated with the production of their behavioral effects. The third specific aim will understand how the alterations of 5-HT release produced by acute stress in the forced swimming test, and modifications of 5-HT neurotransmission produced by antidepressant treatments, are related to the production of the behavioral effects of antidepressant drugs in this test. The results of the proposed work should have important implications for our understanding of the mechanisms involved in the behavioral effects of SSRIs in the clinical treatment of depression.

The overall objective of this proposal is to study how the different types of 5-hydroxytryptamine (5-HT) receptors that have been identified recently by ligand binding techniques regulate discrete behavioral functions which are important to the mechanism of action of antidepressant and antianxiery medications. Chronic administration of different types of antidepressant drugs alter the density of 5-HT receptors. In addition, new anxiolytic drugs, such as buspirone, have been suggested to produce anxiolytic and/or antidepressant effects by pharmacological actions ar the 5-HIlA receptor. The purpose of this proposal is to use animal behavior models associated with the activation of selective types of 5-HT receptors to study pharmacological actions that are important to the therapeutic effects of antidepressant and anxiolytic drugs. Although we have studied unconditioned behaviors elicited by 5-HT agonists as model of 5-HT receptor activation, the present studies will also use conditioned behaviors because they may provide information useful for understanding how humans experience drug effects. Animal are trained to discriminate selective 5-HT agonists and to distinguish the internal state produced by these drugs from drugs with other effects. Since changes in 5-HT 1A and 5-HT2 receptors have been proposed to mediate the effects of antidepressant and anxiolytic drugs will will study discrimination of the 5-HT 1A agonist DPAT and the 5-HT agonist DOB as behavioral models for measuring functional alterations of 5-HT receptor that may be involved in therapeutic effects of these drugs. We will also use information obtained in the above experiments to study the anticonflict effects of 5-HT 1A-selective anxiolytics and to exmaine the involvement of 5-HT receptors in their anxiolytic effects.

This is an application for continuing support for an institutional Training Program in neuropsychopharmacology. Support is requested for five postdoctoral and three predoctoral Fellows yearly. Postdoctoral Fellows in the Program will be either (1)students with doctoral degree in pharmacology, psychology, psychobiology or a related discipline, or (2) physicians who have completed at least three years of specialist training in psychiatry or, in selected instances, other specialty areas (e.g., pediatrics, neurology). Predoctoral fellows will be graduates of a four-year program in biology, chemistry, psychology or a related discipline; upon successful completion of the program, they will receive a doctoral degree in pharmacology or neuroscience. A multidisciplinary program has been developed involving faculty from six departments in the School of Medicine as well as faculty from the Schools of Veterinary Medicine and Arts and Sciences. The faculty members of the Program have a history of collaboration in both teaching and research projects. The aim of the Program is not only to train scientists who will be able to carry out productive research in their individual fields but also to work effectively at the "preclinical-clinical" interface. The objective is addressed by having the postdoctoral Fellows attend specific courses, by arranging for clinical exposure for all non-physicians and by developing interactions between preclinical and clinical investigators. The didactic portion of the Program comprises about 15% of a postdoctoral Fellow's time; most of their time is spent doing research in the facilities of one or more of the 30 faculty members of the Training Program. The approaches and expertise of the faculty are broad and diverse and enable us to provide training at the molecular, cellular, neuroanatomical, animal behavioral and/or clinical level. The predoctoral Fellows are advanced graduate students in pharmacology or neuroscience and take a series of courses designed to provide them with background in the anatomical, biochemical and physiological bases of pharmacology, with an emphasis on neuropsychopharmacology. Specific courses have been developed to meet these goals. Although a standard curriculum has been devised, the Training Program is structured so that it can be modified to fit the particular needs and career plans of each individual student. The goal of the Training Program is to supplement the research program of graduate student with activities (seminar presentations, colloquia) that emphasize the consideration of clinical practice in psychiatry in the conduct of basic research.

DESCRIPTION OF OVERALL PROJECT (provided by applicant) : The overall goal of this Program Project Grant is to investigate how serotonergic neurotransmission modulates many important behaviors. Abnormalities in 5-hydroxytryptamine (5-HT, serotonin) neurotransmission have been implicated in the pathogenesis of diverse psychiatric disorders, and various classes of psychotherapeutic agents have prominent effects of different aspects of synaptic transmission mediated by 5-HT. Studies in this Program Project Grant specially focus on the function of 5-HT1A receptors because of their role in mediating the effects of serotonergic antidepressant and anti-anxiety drugs. This Program Project Grant employs a multi-disciplinary approach to study a number of outstanding critical questions concerning the role of 5-HT1A receptors in modulating serotonergic neurotransmission at the behavioral systems, cellular and molecular levels of analysis. A common theme developed by all of the projects in the Program is that molecular genetics now provides the technology to alter the function of genes that are associated with specific neurotransmitter receptors in mammals. Recently developed tissue-specific and inducible knockout preparations provide the ability to address novel questions concerning the developmental neurobiology and neural circuitry of 5-HT linked to behavior in novel and creative ways. Another common theme appearing in all of the projects is the need to elaborate the role of individual 5-HT circuits that contribute to the developmental expression of emotional behaviors or to the action of psychotherapeutic drugs, such as the SSRIs. The functional significance of this circuitry will be established by systematically comparing the properties of 5-HT receptors in different 5-HT circuits using behavioral, in vivo microdialysis, electrophysiological, and molecular genetics techniques. Taken together, the integrative studies of this Program Project Grant will provide new information on the biology of serotonin in behavior and psychopathology with an emphasis on genetic regulation, neural circuitry and the pharmacology of antidepressant drugs. The results of the proposed work should have important implications for our understanding of synaptic transmission in the brain and of the effect of psychotherapeutic drugs.

The increased need to treat illicit users of cocaine, and other psychomotor stimulants, requires understanding the neural substrates of its effects that are associated with drug withdrawal and residual craving that could lead to relapse. The results of conditioning experiments with animal models and human drug users have suggested that environmental stimuli associated with the injection of stimulants may come to elicit similar responses as the drug itself. these conditioned environmental stimuli associated with drug administration may contribute to drug craving and eventual relapse by producing physiological and neurochemical changes during a critical period following drug withdrawal. Examples of such stimuli in human addicts include drug-taking paraphernalia or the sight of a bar of place associated with taking drugs. The technique of in vivo microdialysis, which allows the direct measurement of neurotransmitter release, provides a method to examine the neural substrates that underlie conditioned drug effects. When these experiments are carried out in awake freely-moving animals, behavioral evidence for conditioned drug effects can be examined simultaneously with associated neurochemical changes. Although the pharmacology of cocaine has been studied extensively, little is known about the neural substrates underlying the conditioned effects of cocaine, which may provide important targets for understanding drug relapse or for designing potential pharmacotherapies that may treat drug relapse. The technique of in vivo microdialysis will be used to examine the release of dopamine, norepinephrine and serotonin in the nucleus accumbens, the brain region most implicated in the reinforcing effects of cocaine and amphetamine, in three different series of behavioral conditioning studies thought to be mediated by the nucleus accumbens. Repeated administration of cocaine or amphetamine sensitizes rats to their effects on subsequent injections provided that the environment cues associated with drug administration remain constant. The first series of studies will examine the influence of testing environment on the development of sensitization to the neurochemical and behavioral effects of cocaine and amphetamine following their repeated administration. The second series of studies will examine neurotransmitter release following the training and during the expression of conditioned place preference. Conditioned place preference provides a behavior thought to be associated with the rewarding effects of drugs where rats choose to remain n an environment that has previously been associated with injections of cocaine or amphetamine. The third series of studies will examine neurotransmitter release during responding for the presentation of secondary reinforcers that have been associated with the self-administration of cocaine or amphetamine. The presentation of secondary reinforcers, such as brief visual stimulus, associated with injections of cocaine or amphetamine can maintain lever pressing behavior even after the primary reinforcing effects of drug injections have been extinguished. These studies taken together will provide important new information concerning whether conditioned drug effects in rats and their neural substrates in the nucleus accumbens are sufficiently robust and persistent to provide a model for residual drug craving in drug addicts. Conditioned drug effects and their neurochemical substrates may then be considered targets for pharmacological intervention as residual effects of drug addiction that contribute to relapse during therapy.

Behavioral and electrophysiologic studies suggest that the regulation of serotonin (5-HT) release may be involved in the clinical effects of new psychotherapeutic drugs, particularly 5-HT uptake inhibitors such as fluoxetine that are antidepressants and 5-HT(1A) receptor agonists such as buspirone that are anxiolytics and antidepressants. Evidence suggests that chronic administration of SSRIs produces desensitization of presynaptic 5-HT(1A) receptors that may account for, at least in part, the lag time between the initiation of drug treatment and the appearance of therapeutic effects. In addition, clinical studies suggest that coadministration of antagonists of 5-HT(1A) autoreceptors can potentiate the clinical effects of SSRIs. The new technique of in vivo microdialysis permits the release of 5-HT to be measured in discrete brain regions in awake unrestrained animals. This technique is ideally suited to directly study the ability of psychotherapeutic drugs to regulate the ability of presynaptic 5-HT(1A) receptors to modify 5-HT release and to determine whether altered 5-HT release is involved in their behavioral effects. The first goal of this project will be to establish the time course for the ability of SSRIs and MAOIs to regulate the release of 5-HT in the striatum and hippocampus by modifying the function of presynaptic 5-HT(1A) autoreceptors. Additional studies will examine the time course of recovery of 5-HT(1A) receptor sensitivity after the discontinuation of drug treatment. Radioligand binding studies will examine changes in the density of 5-HT(1A) receptors in the raphe that are coupled to G proteins using new selective ligands developed by this Program. Additional studies will examine the ability of chronic administration of 8-OH-DPAT to 1) modify the function of 5-HT(1A) autoreceptors that regulate 5-HT release in the striatum and hippocampus and 2) to evaluate changes in the ability of SSRIs to increase extracellular 5-HT after prior treatment. Finally, the ability of coadministration of antagonists that are selective for 5-HT(1A) and 5-HT(1B) receptors to modify the effects of SSRIs on extracellular concentrations of 5-HT after and chronic administration of SSRIs will be studied. The results of the proposed work should have important implications for our understanding of synaptic transmission in the brain and of the effects of psychotherapeutic drugs.

DESCRIPTION (provided by applicant): The overall hypothesis of this proposal is that regional variations in 5-HT release are important determinants of the response to SSRIs and behavioral reactivity to stress and environmental stimuli. The results for our prior in vivo microdialysis and behavior studies in 5-HT receptor mutants guide the objectives for this renewal proposal. The first objective is to employ targeted pharmacological challenge procedures to establish that 5-HT efflux in different brain regions is regulated in a topographical pattern and to determine the extent that different 5-HT autoreceptors contribute to these regional effects. The second objective is to provide new information concerning the circuitry by which 5-HT1A receptors regulate 5-HT transmission and compensations for their absence using tissue specific and temporally inducible genetic deletion. The third objective will be to examine the efflux of 5-HT in different brain regions of wild-type and mutant mice during performance of behaviors on tests for anxiety and antidepressants. The final objective will be to examine interactions with catecholamine neurotransmitters that may be important for regulating 5-HT efflux. Taken together, the proposed research program will continue to examine systematically the utility of genetic regulation for determining specific changes in 5-HT release and behavior is that is related to the expression of affective behaviors and the effects of antidepressant drugs.

[unreadable] DESCRIPTION (provided by applicant): The purpose of this proposal is to develop and establish a National Cooperative Drug Discovery Group for the Treatment of Mood Disorders (NCDDG-MD) between investigators in the Center for Neurobiology and Behavior at the University and in the Division of Neuropharmacology at Wyeth Research Laboratory. The goal of this program is to provide a critical advance in drug discovery for mood disorders by focusing and combining the expertise of investigators from each institution on a problem of mutual interest and importance to the field. The program foundation emerges from morphological and molecular evidence that prolonged exposure to stress and depression produces neuronal atrophy and that chronic administration of antidepressant drugs to animals produce changes in neuronal proliferation and molecular markers for neurotrophic factors in the hippocampus that has only been discovered recently. These morphological effects may be key physiological elements that produce or sustain behavioral recovery during remission after chronic administration of antidepressants to patients. The focus of the NCDDG research program will be to develop this key idea as a paradigm for drug discovery in mood disorders. This will be done by establishing that the functional consequences of changes in neuroplasticity produced by chronic antidepressant drug treatment are important for the reversing the detrimental effects of stress on neural remodeling and sustaining behavioral recovery. The experimental program will examine the relationship between the morphological and behavioral consequences of multiple types of antidepressant drug treatments given to rats and mice exposed to stressors that have been demonstrated to be relevant for measuring antidepressant drug responses. Secondly, critical hypotheses concerning the functional relationship between hippocampal cell proliferation and the behavioral consequences of antidepressant drug treatments will be tested by employing novel genetic models. Finally, potentially novel classes of antidepressant drugs will be tested using the developed procedures. Because stress may contribute to the pathophysiology of mood disorders by causing neuronal atrophy and altering cell morphology, increased neurogenesis could contribute to the actions of antidepressant treatment by facilitating neural plasticity and remodeling critical for behavioral recovery from stress. The development of protocols demonstrating that reversal of the functional consequences of neuronal remodeling in animals subjected to stress leads to behavioral recovery will enable the discovery of potentially novel antidepressant drugs. [unreadable] [unreadable]

DESCRIPTION (provided by applicant): This proposal examines how the regulation of adult neurogenesis produced by repeated antidepressant drug treatment in mice may contribute to behavioral recovery from stress and depression. Major depressive disorder results from convergent underlying genetic predispositions and exposure to environmental stress. Evidence for increases of neurogenesis in the adult dentate gyrus of the hippocampus is a model for changes in neuroplasticity that emerge with chronic treatment with antidepressant drugs and serve as a model for the production of therapeutic effects. Most studies have measured the effects of antidepressants using rodents under routine housing conditions and have ignored the critical role of genetics and stress in contributing to drug treatment effects. We have identified a mouse strain (MRL/MpJ) that shows larger increases in neurogenesis following chronic fluoxetine. Also, the addition of stress hormones augments the effects of fluoxetine on neurogenesis in a non-responder mouse strain (C57BL/6). The central hypothesis of this grant proposal is that genetic predispositions and stress produce a critical role for revealing the effects of chronic antidepressant treatments on hippocampal neurogenesis. The use of flow cytometry as a technique to measure neurogenesis rapidly developed by this laboratory will enable completion of the large number of studies required for investigation of the pharmacology of neurogenesis. The primary goals of this proposal are: 1) demonstrate the critical role of exposure to corticosterone (CORT) in augmenting responses to chronic treatment with antidepressant drugs on neurogenesis and behavior in a responder and non-responder mouse strain;2) show whether environmental stress plays a similar role in causing antidepressant drugs to alter neurogenesis and behavior;and 3) determine whether hippocampal BDNF serves as a mechanism underlying the production these effects by chronic antidepressant drug treatments. PUBLIC HEALTH RELEVANCE: This project examines the convergent role of genetic predispositions and exposure to environmental stress in mouse models regulating the effects of chronic antidepressant drug treatments on hippocampal neurogenesis and behavior. Major depression is an important public health problem because of its severe economic impact and contribution to morbidity from other medical disorders. The results of this project will contribute to identifying mechanisms of vulnerability and resilience to stress and lead to the discovery of novel and more effective antidepressant treatments.

DESCRIPTION (provided by applicant): The overall goal of this research program is to evaluate the therapeutic potential for buprenorphine and to use animal studies to support its development for depression and anxiety disorders. There is a clear medical need for new drugs that would expand the options for treating comorbid depression and anxiety, especially for the substantial number of patients' refractory to current medications. Buprenorphine is medically available and used safely for the treatment of physical dependence to opioids but has received virtually no attention for the use of psychiatric disorders in nondependent populations. As a mu-opioid receptor (MOR) partial agonist and kappa-opioid receptor (KOR) antagonist, buprenorphine has been studied extensively in models of drug reward, physical dependence, and analgesia. Recent studies highlighting the role of dynorphin in stress have shown that KOR antagonists can produce antidepressant and anxiolytic effects in animal models. The pharmacological profile of buprenorphine as a potent MOR partial agonist and KOR antagonist supports the likelihood that buprenorphine would produce beneficial effects on stress-induced behaviors. Few published studies on the effects of buprenorphine in animal models of depression and anxiety exist to support clinical trials and development or to understand its potential mechanism of action. Taken together, these experiments will establish a basic foundation for considering the development of buprenorphine for new indications in psychiatric disorders and translate to prospective clinical treatment studies of depression and anxiety in treatment-resistant patients.

? DESCRIPTION (provided by applicant): The overall goal of this research program is to determine whether kappa opioid receptor antagonists have the potential to be developed as rapidly acting antidepressants. There is a clear medical need for new drugs that would expand the options for treating comorbid depression and anxiety, especially for the substantial number of patients refractory to current medications. Kappa opioid receptors and their endogenous ligand dynorphin are thought to be involved in the production of dysphoria and depression accompanying exposure to stress. Kappa opioid receptor antagonists can produce antidepressant and anxiolytic effects in animal models, but the pharmacological profile of existing compounds make them unsuitable for clinical development. The proposed studies would evaluate the effects of two novel kappa opioid receptors, LY2456302 and LY2444295, as potential antidepressant and anxiolytic drugs using animal behavior tests. Studies will determine whether the kappa opioid receptor antagonists produce their effects more rapidly than established antidepressants and similar to ketamine on tests such as the forced swim test, novelty-induced hypophagia and on acutely reversing the effects of chronic mild stress on anhedonia and anxiety. The mechanism of action of kappa opioid receptor antagonists will be confirmed using mice with constitutive deletion of kappa opioid receptors. Additional studies will identify the neural circuitry involved in producing these behavioral effects. Taken together, these experiments will strengthen a basic foundation for considering the development of a novel kappa opioid receptor antagonists as rapid acting antidepressants for eventual therapy in treatment-resistant depression.