Terry E. Robinson - US grants

It is well established that the repeated administration of stimulant drugs (e.g. amphetamine) results in a progressively enhanced behavioral response to subsequent injections. This phenomenon of 'reverse tolerance', or sensitization, has generated considerable interest because it is thought to provide an animal analogue of amphetamine (AMPH) psychosis in humans. However, a single injection of AMPH may also produce a long-lasting change in brain activity. In preliminary studies using AMPH-induced rotational behavior as an index of mesostriatal dopamine (DA) activity we found that a single injection of a low dose (1.25 mg/kg) of AMPH greatly enhanced the rotational behavior produced by a second injection of AMPH given 3-4 weeks later in intact female, ovariectomized female and castrated male rats. Intact males did not show as robust a change. This behavioral sensitization may be due to changes in DA release, since it is accompanied by a long-lasting enhancement in AMPH-stimulated endogenous DA release from striatal tissue in vitro. The studies proposed here are disigned to: (1) further characterize the phenomenon of long-term changes in rotational behavior produced by a single or repeated injections of AMPH: (2) examine the role of gonadal steroid hormones in modulating this form of neural plasticity; (3) further explore the possibility that long-lasting changes in DA release from terminals in a variety of brain regions are involved in the development of behavioral sensitization; (4) determine whether similar long-lasting changes in brain activity are produced by other stimulant drugs; and (5) determine whether a single injection of AMPH will produce comparable changes in other behaviors thought to be mediated by brain DA systems. We believe the proposed studies integrating both in vivo and in vitro approaches will increase our understanding of the basic neurobiological mechanisms involved in neuroplasticity. The studies are of clinical interest since they may provide some insight as to the neurochemical changes underlying AMPH psychosis. Lastly, the fact that the single administration of psychostimulant drugs may result in long-term physiological alterations should be of obvious practical concern in psychotherapeutics.

We have used amphetamine (AMPH)-induced rotational behavior as an index of mesostriatal dopamine (DA) activity. In preliminary studies we found that a single injection of a relatively small dose of AMPH (1.25 mg/kg) greatly enhanced (nearly doubled) the rotational behavior produced by a subsequent injection of AMPH given 3-4 weeks later. This long-lasting facilitation of rotational behavior occurred only in intact female, ovariectomized female and castrated male rats; not in intact males. We have hypothesized that an androgen (probably testosterone) suppresses the development of this form of neuroplasticity. Another factor which influenced sensitization was the stability of an endogenous asymmetry in the nigrostriatal DA system. We have evidence that these long-lasting behavioral changes produced by AMPH are due to long-term changes in striatal DA release. A month after a single pretreatment with AMPH the AMPH-stimulated release of DA from striatal tissue in vitro was significantly enhanced, relative to saline pretreated controls. The studies proposed here are designed to: 1) further characterize the phenomenon of long-term changes in rotational behavior produced by single or repeated injections of AMPH; 2) examine the role of gonadal steroid hormones in modulating this form of neural plasticity; 3) further explore the possibility that long-term changes in the mesostriatal DA system are involved in the development of behavioral sensitization by using an in vitro perifusion system to study endogenous DA release; and 4) determine whether a single injection of AMPH will produce comparable changes in other behaviors thought to be mediated by brain DA systems. We believe the proposed studies integrating both in vivo and in vitro approaches will increase our understanding of the basic neurobiological mechanisms involved in neuroplasticity. The studies are of clinical interest since sensitization is thought to provide an animal model of the neurochemical changes which underlie amphetamine psychosis and/or paranoid schizophrenia in man. Lastly, the fact that the single administration of psychostimulant drugs may result in long-term physiological alterations is of obvious practical concern in psychotherapeutics.

The repeated use of psychomotor stimulant drugs, such as amphetamine (AMPH), results in both transient and persistent changes in behavior, affect and cognitive function following the sudden discontinuation of drug use. In humans behavioral changes include (1) transient post-AMPH withdrawal depression, (2) a persistent hypersensitivity to environmental stimuli associated with AMPH use, leading to drug craving, and (3) a persistent sensitization to the psychotogenic effects of AMPH. It is hypothesized that these behavioral manifestations of AMPH withdrawal are due, at least in part, to neurochemical adaptations in brain catecholamine (CA) systems produced by repeated drug exposure. Very little is known, however, about the nature of these neurochemical adaptations, their relation to behavior, how they change as a function of time following withdrawal, or how they are altered by putative pharmacotherapies. These questions are very difficult to address in humans. The overall aim of this proposal, therefore, is to use an animal model to characterize the changes in CA neurotransmission associated with different aspects of the AMPH withdrawal syndrome. Changes in CA neurotransmission will be assessed in a number of brain regions by use of on-line automated intracerebral microdialysis in freely moving rats. This technique will allow us to relate changes in the extracellular concentration of dopamine (DA) and norepinephrine (NE) to ongoing behavior across the entire day-night cycle. Specific experiments are designed to characterize the relationship between changes in CA neurotransmission and (1) post-AMPH withdrawal behavioral depression (nocturnal hypoactivity), (2) the behavioral hypersensitivity to environment cues associated with AMPH treatment (conditioned incentive stimuli), and (3) the behavioral hypersensitivity to a subsequent AMPH challenge (behavioral sensitization) -- all as a function of time following the discontinuation of treatment with escalating doses of AMPH. Finally, a variety of pharmacotherapies have been proposed for stimulant drug abuse, but nothing is known about how the neural adaptations produced by repeated exposure to AMPH influence the action of these agents, or vice versa. Therefore, experiments are proposed to determine the interaction between potential pharmacotherapeutic agents and both transient behavioral depression and persistent behavioral sensitization, and their related changes in CA neurotransmission. Furthermore, there is reason to suspect that some agents that are effective in alleviating transient depressive symptoms may later exacerbate stimulant craving or sensitization, and such interactions also will be studied. In conclusion, the experiments proposed here will be important for understanding the long-term effects of chronic stimulant drug use on brain CA systems, and in developing an animal model to test the ability of putative pharmacotherapeutic agents to 'normalize' brain CA systems and behavior during stimulant withdrawal.

[unreadable] DESCRIPTION (provided by applicant): [unreadable] This application is a request for continuing support for a predoctoral NIDA Training Program in Neuroscience, which was founded at The University of Michigan (DM) in 1995. The major goal of the Program is to recruit and develop student interest in research related to the biological basis of substance abuse, and to provide the necessary administrative, faculty and educational resources for students with these interests to pursue a Ph.D. degree in the field of neuroscience. [unreadable] [unreadable] To be eligible for support by the NIDA Training Program students first must gain admittance to an existing DM graduate program in the biological, biomedical or natural sciences, such as the Interdepartmental Graduate Program in Neuroscience. Students nominated for support by the NIDA Training Program in Neuroscience are selected on the basis of two criteria: (a) academic qualifications and references (ie., academic excellence), and (b) the relevance of their program of study and research to the NIDA mission. After admission to the NIDA Training Program students pursue a program of study in the basic neurosciences, including a required course on the neuropsychopharmacology of substance abuse. The faculty in the NIDA Training Program in Neuroscience consist of (a) Fifteen Core NIDA Training Faculty, all of whom have research interests in the biological basis of substance abuse. Most of these faculty are PI or Co-Pi on a NIDA-funded research grant. Students in this Program are expected to conduct their dissertation research with one of the Core NIDA Training Faculty. Collectively, the Core NIDA Training Faculty provide considerable expertise in the neurobiology and biopsychology of many drugs

This application is for a Senior Scientist Award (K05) to provide salary support for Terry E. Robinson to continue his ongoing studies on neuroplastic adaptations engendered by drugs of abuse and the role they play in addiction. Dr. Robinson has published extensively on the effects of psychomotor stimulants on brain monoamine systems and behavior, and especially on psychomotor stimulant sensitization, withdrawal, and neurotoxicity. Recently he has focused on the ability of environmental stimuli to modulate the induction and expression of psychomotor sensitization, as well as the neurobiological mechanisms involved. The experiments proposed in the present application represent a new research direction. Most studies on the neurobiology of sensitization have focused on biochemical adaptations in neurotransmitter systems. Drs. Robinson and Kolb have recently reported, however, that repeated treatment with amphetamine or cocaine produces persistent changes in the structure of dendrites and dendritic spines on neurons in the nucleus accumbens and prefrontal cortex, two brain regions prominently implicated in mediating drug reward. These findings suggest that exposure to psychostimulant drugs alters patterns of synaptic connectivity in these brain regions, presumably also altering their function. The specific aim of the new research direction proposed here is to further characterize the ability of psychostimulant drugs to alter neural circuitry in brain reward regions (using the Golgi technique) and to determine the extent to which these structural adaptations are related to the development of psychomotor sensitization. In the first series of experiments a variety of procedures known to increase or decrease the strength or persistence of behavioral sensitization will be used to determine the extent to which structural adaptations co-vary with the behavioral phenomenon. In the second, it will be determined whether drug self-administration experience produces effects on dendritic structure similar to those seen with experimenter- administered drug, and the relationship between the degree of exposure to self-administered cocaine, escalation of intake and morphological adaptations. In the third, more detailed information will be acquired about the exact locus of psychostimulant drug-induced changes in spine density on medium spiny neurons and pyramidal cells (i.e., are structural changes confined to one portion of the dendritic tree), and whether other cell populations are also affected. Finally, in the fourth, it will be determined whether exposure to psychostimulant drugs at one point in life limits the ability of the affected brain regions to undergo structural adaptations later in life, as a consequence of changes in environmental condition or in association with recovery from brain damage. For Dr. Robinson these experiments involve a new approach to the study of psychomotor sensitization, and to the problem of the long-term neurobiological consequences of drug use. This is the reason for a KO5 application at this time. A KO5 Award would free his time from other departmental and university responsibilities and allow him to concentrate on developing new skills in the anatomical and molecular analysis of persistent drug effects.

DESCRIPTION: The repeated administration of psychostimulant drugs, such as amphetamine or cocaine, produces persistent behavioral and neurobiological adaptations that are thought to contribute to the long-term sequelae associated with drug abuse, including tolerance, sensitization, dependence and addiction. One form of neurobehavioral adaptation implicated in addiction is represented by the phenomenon of behavioral sensitization, whereby past drug exposure renders individuals hypersensitive to the psychomotor activating and incentive motivational effects of drugs. The overall aim of this application is to better understand the long-term neurobiological consequences of repeated exposure to psychostimulant drugs, the role these play in the development of behavioral sensitization, and their implications for addiction. More specifically, we have recently found that repeated treatment with amphetamine or cocaine produces persistent changes in the structure of dendrites and dendritic spines on neurons in the nucleus accumbens and prefrontal cortex, two brain regions prominently implicated in mediating drug reward. These findings suggest that exposure to psychostimulant drugs alters patterns of synaptic connectivity in these brain regions, presumably also altering the function of this neural circuitry. A specific aim of this application is to further characterize the ability of psychostimulant drugs to alter neural circuitry in brain reward regions (using the Golgi technique) and to determine whether these structural adaptations are related to the development of psychomotor sensitization. In one series of experiments we will use a variety of procedures known to increase or decrease the strength or persistence of behavioral sensitization to accumulate converging evidence regarding the extent to which structural adaptations co-vary with the behavioral phenomenon. In other experiments we will acquire more detailed information about the exact locus of psychostimulant drug-induced changes in spine density on medium spiny neurons and pyramidal cells (i.e., are structural changes confined to one portion of the dendritic tree), and whether other cell populations are also affected. In addition, we will determine whether drug self-administration experience produces effects on dendritic structure similar to those seen with experimenter-administered drug, and the relationship between the degree of exposure to self-administered cocaine, escalation of intake and morphological adaptations. Finally, in the last year of the award period we will expand the scope of our investigations to study the implications of drug-induced plasticity for other forms of experience-dependent plasticity. Specifically, we will test whether exposure to psychostimulant drugs at one point in life limits the ability of the affected brain regions to undergo structural adaptations later in life, as a consequence of changes in environmental condition or in association with recovery from brain damage.

Cocaine Impact on Plasticity &Dendrite Morphology: Interaction with Environmental Complexity One of the most compelling examples of experience-dependent behavioral plasticity, whereby experience at one period in life changes behavior for a lifetime, is addiction. The propensity of addicts to relapse, even months to many years after the discontinuation of drug use,and long after withdrawal symptoms have subsided, provides stark evidence that drug use has long lasting consequences for behavior and psychological function. Similarly, very long-lasting changes in brain and behavior have been found in animal models, for example, following sensitization. Persistent experience-dependent changes in behavior and synaptic organization are presumably due to the effects of drugs and other experiences acting via coordinated actions on a variety of plasticity-related genes, and perhaps by influencing neurogenesis. Indeed, there is now considerable evidence that drugs of abuse usurp many of the same cellular and molecular mechanisms responsible for experience-dependent plasticity. This raises the hypothesis that changes in synaptic organization produced by experience may interact with those produced by exposure to drugs of abuse. The overall aim of this project is to explore the interaction between the effects of exposure to a drug of abuse, cocaine, and the effects of another life experience (living in a relatively complex environment), on the expression of key plasticity-related genes and on adult neurogenesis, in two genetically-distinct populations of rats that vary in their susceptibility to cocaine. Studies to date support the hypothesis that exposure to psychostimulant drugs may,under some circumstances and in some brain regions, saturate the potential for future plasticity (or produce "metaplasticity") and thus occlude the ability of subsequent experiences to induce molecules necessary for synaptic reorganization. The hypothesis that exposure to psychostimulant drugs may limit the potential for future plasticity in response to changes in environmental condition has important clinical implications. If true, it would suggest that the repeated use of some drugs of abuse might limit the ability to adapt positively to changes in environmental circumstances. Thus, some of the neuropsychological deficits seen in addicts could be due to limits on synaptic plasticity imposed by past druguse.

0-11 years old; 3-10C; AMCF-I; Age; Air; Bronchiectasis; CAT Scan, X-Ray; CAT scan; CRISP; CT X Ray; CT scan; CXCL8; Child; Child Youth; Children (0-21); Children with CF; Clinical; Computed Tomography; Computer Retrieval of Information on Scientific Projects Database; Computerized Axial Tomography (Computerized Tomography); Computerized Tomography, X-Ray; Drugs; EMI scan; Elastase; Elastases; Funding; Future; GCP-1; GCP1; Grant; Human, Child; IL-8; IL8; IL8 gene; Image; Institution; Intervention Trial; Investigators; K60; LECT; LUCT; LYNAP; Lung; Lung diseases; MDNCF; MONAP; Measurement; Medication; Mucous body substance; Mucus; NAF; NIH; National Institutes of Health; National Institutes of Health (U.S.); Natural History; Outcome Measure; Pancreatic Elastase; Pancreatic Elastase I; Pancreatopeptidase; Pharmaceutic Preparations; Pharmaceutical Preparations; Pulmonary Diseases; Pulmonary Disorder; Research; Research Personnel; Research Resources; Research Specimen; Researchers; Resources; Respiratory Disease; Respiratory Disorder; Respiratory System Disease; Respiratory System Disorder; Respiratory System, Lung; SCYB8; SUBGP; Score; Source; Specimen; Spirometry; Sputum; Subgroup; TSG-1; Thick; Thickness; Tomodensitometry; Tomography, Xray Computed; United States National Institutes of Health; Visual; X-Ray Computed Tomography; airway epithelium infalmmation; airway inflammation; b-ENAP; base; catscan; children; children with cystic fibrosis; computed axial tomography; computerized axial tomography; computerized tomography; design; designing; drug/agent; imaging; lung disorder; mucous; pancreatopeptidase E; prospective; pulmonary; pulmonary function; trial comparing; youngster

PROJECT SUMMARY (See Instructions): The Administrative Core will provide administrative oversight of the entire Program Project. This will include not only budgetary and scientific oversight and coordination of individual Projects and the Behavioral Core, but also organization of meetings and interactions with the Scientific Advisory Committee [Drs. Kent Bemdge (University of Michigan), Regina Carelli (University of North Carolina) and Ron See (Medical University of South Carolina)], and coordination with our Statistical Advisor, Dr. Ed Rothman (University of Michigan).

PROJECT SUMMARY (See instructions): Addicts have great difficulty resisting stimuli (cues) that have been associated with drug use. Such cues unduly attract their attention, draw them to locations where drugs are located and motivate continued drug seeking behavior - often leading to relapse even in the face of an expressed desire to discontinue drug use. Drug cues are thought to acquire incentive motivational properties (incentive salience) as a consequence of Pavlovian conditioning, whereby previously neutral stimuli acquire conditional stimulus (CS) properties. However, in preclinical studies using rats we have discovered that individuals vary markedly in the extent to which they attribute incentive salience to reward cues. A reward cue may act as a perfectly effective CS, evoking a conditional response (CR) in all animals, but function as a potent incentive stimulus only in some. Only if reward cues act as incentive stimuli do they come to attract, incite, provoke, spur and motivate, leading to potentially maladaptive behavior. We hypothesize, therefore, that individuals prone to attribute incentive salience to reward cues will have particular difficulty resisting them and will be especially vulnerable to develop addiction-like behavior. We propose a series of preclinical studies using rats to test this hypothesis, and to determine the relationship between this trait, and others thought to confer vulnerability to addiction, including a propensity to make impulsive actions'. Specific studies address the following key questions: (1) Is it possible to predict, prior to any drug experience, which individuals will attribute incentive salience to a drug cue? (2) Does variation in the propensity to attribute incentive salience to reward cues predict which individuals are susceptible to develop addiction-like behavior when they are given extended opportunity to self-administer drugs? (3) Does past experience with drugs increase the degree to which incentive value is attributed to drug cues? (4) Do the brain regions necessary for Pavlovian stimulus-reward learning differ in animals that do or do not attribute incentive salience to reward cues? These studies have the potential to fundamentally shift how we think about individual vulnerability to addiction, and point the way for better-targeted interventions.

DESCRIPTION (provided by applicant): Much of our daily behavior is controlled by stimuli (cues) associated with rewards that promote survival - for example, they attract us to sources of food and to potential mates. However, such cues can also promote maladaptive behavior. Food cues can instigate overeating, and cues associated with drug rewards motivate drug use and instigate relapse, thus contributing to addiction. Cues associated with rewards (conditional stimuli, CSs) powerfully motivate both normal and maladaptive behavior only if they are attributed with incentive motivational properties (incentive salience), and thus acquire the ability to act as incentive stimuli. In preliminary studies we made two novel observations: (1) the conditional stimulus properties of reward cues are not sufficient for them to also act as incentive stimuli, and (2) there is large variation in the propensity of individual rats to attribute incentie salience to food and drug cues, and thus to motivate behavior. These two observations lead to an innovative hypothesis, never explored, which is that individuals prone to attribute Incentive salience to drug cues will have particular difficulty resisting such cues, and thus be especially vulnerable to addiction. The purpose of this Program Project is to test this hypothesis, to study the operation of neurobiological systems that may underlie this variation, and to determine the relationship between this phenotype and other traits that may confer vulnerability to addiction. Thus, Project 1 primarily involves behavioral studies to determine if it is possible to predict, pror to any drug experience, which individuals are prone to attribute incentive salience to drug cues and whether these individuals are especially likely to develop addiction-like behavior. Project 2 focuses on whether this individual variation is related to variation in dopamine signaling in the nucleus accumbens, using fast scan cyclic voltammetry, and Project 3 uses electrophysiological recordings to determine whether this is further reflected in neural encoding in the main output of the accumbens, the basal forebrain/ventral pallidum. Finally, Project 4 links these subcortical systems with cortical, cognitive control systems and will explore cortical mechanisms that may account for cognitive vulnerabilities in individuals prone to attribute incentive salience to rewar cues.

Abstract: It is generally accepted that limited (Short Access, ShA) cocaine self-administration experience does not produce changes in brain and behavior associated with addiction. The most widely used models of addiction involve Long Access procedures (LgA, 6hrs+/day), which greatly increase the amount of drug consumption. LgA produces a number of addiction-like behaviors, and changes in brain, not seen with ShA. However, in addition to the amount of cocaine use, the temporal pattern of use ? how intermittent it is ? is also important in producing addiction-like behavior and associated neuroadaptations. Zimmer et al. (2013) developed an intermittent access self-administration procedure (IntA) to better model the intermittent patterns of cocaine use seen in addicts. He found that, despite much less total drug consumption, motivation for cocaine was higher in rats with prior IntA experience than those with LgA experience. Consistent with this, we found that IntA produces robust incentive-sensitization, as indicated by a progressive increase in cocaine demand (based on behavioral economic indicators), an associated escalation of intake, and very robust reinstatement of cocaine seeking behavior ? despite consuming much less drug than under LgA conditions. Thus, our Overall Aim is to directly compare and contrast the behavioral, psychological and neurobiological effects of these two models of addiction. The overall goal is to determine whether the changes in brain and behavior produced by LgA vs. IntA experience only differ quantitatively, or, whether there are qualitative differences in outcomes. This information will be critical in making informed decisions about the animal model to use in preclinical studies of addiction, and will also be important in determining directions in the development of therapeutics.