Linda J. Porrino - US grants

DESCRIPTION: (from applicant's abstract) Although alcohol abuse and alcoholism are significant health problems in our society, our understanding of the neurobiological actions of alcohol in the central nervous system remains incomplete. The overall goal of our research continues to be the expansion of knowledge of the neuroanatomical basis of the effects of alcohol using neuroimaging methods. During the past funding period we have demonstrated that the neuroanatomical circuits activated by the administration of alcohol are dependent on the dose of alcohol, as well as the length of time since ingestion. In addition, we have identified a circuit comprised mainly portions of the mesocorticolimbic system that mediates the effects of alcohol self-administration. The purpose of the studies proposed here is to build on this work, thereby extending our understanding specifically of the neural substrates of alcohol self-administration. Using the quantitative auto-radiographic 2- [14C]deoxyglucose method, our studies will, first, identify the role of the dose of alcohol in determining the characteristics of the circuitry underlying self-administration. Second, changes in the pattern of functional activation that result from a longer post-ingestion intervals after self-administration will be determined. A third goal of these studies is to identify the neuroanatomical substrates of the anticipatory response to alcohol. Metabolic mapping will be applied to rats in the presence of cues that predict the availability of alcohol. The final goal of these studies to determine the circuits through which dopamine is involved in the voluntary ingestion of alcohol. The studies proposed in the present application focus on the definition of the neural circuitry that mediates various aspects of the alcohol self-administration by combining neuroimaging methods with well-controlled behavioral paradigms in order to further our understanding of the effects of alcohol in behaviorally relevant contexts.

The proposed experiments are directed toward an understanding of the neuroanatomical and neurochemical substrates of the long-lasting behavioral, cognitive, physiological, and neurobiological consequences of chronic cocaine abuse. This phenomenon, called behavioral sensitization is a complex process that can be significantly influenced by a number of non-pharmacological variables including the presence of conditioned environmental cues. Conditioned effects are also thought to be important determinants of human drug abuse, particularly in such phenomena as drug craving and relapse. The effects of conditioned environmental cues on repeated cocaine administration most likely are mediated by neuronal circuits different from those that mediate the unconditioned consequences of repeated administration. The proposed experiments are designed to characterize further the neuroanatomical substrates of behavioral sensitization with a specific focus on the influence of conditioned cues in this process. Specifically, the quantitative 2-[14C]deoxyglucose autoradiographic method will be used to identify in rats 1) the brain regions that mediate cocaine-induced behavioral sensitization in the presence and absence of conditioned environmental stimuli, 2) the dose-dependent effects of repeated cocaine administration, 3) the time course of development of conditioned behavioral sensitization, and 4) the persistence of the effects of conditioned behavioral sensitization following withdrawal from cocaine treatment. A second goal of the proposed studies is to determine the neurochemical changes that underlie the changes in functional activity observed in the metabolic mapping studies. First, quantitative receptor autoradiography will be used to measure alterations in dopaminergic and opioid receptor systems. Measurements of receptor density will be made in the same animals used in the 2-deoxyglucose studies, permitting the systematic evaluation of the effects of dose, duration of treatment, presence of conditioned cues, and length of time following withdrawal from drug treatment on receptor number. Second, in vivo microdialysis will be used to measure the effects of repeated cocaine administration in the presence of conditioned environmental cues on concentrations of extracellular dopamine in the nucleus accumbens. The relationship between dopamine concentrations and rates of glucose utilization in this nucleus will be investigated by combining 2-deoxyglucose and in vivo microdialysis measures in rats chronically treated with cocaine. These studies have important implications for the understanding of the long term sequelae of chronic cocaine abuse. Furthermore, they will provide a more comprehensive analysis of the role of conditioned environmental cues in chronic drug abuse and may provide a more extensive basis for the development of behavioral and pharmacological strategies for treatment.

Much of our understanding of the neurobiological basis of cocaine abuse in humans has been based on investigations carried out in rodents. It has been only recently that studies imaging living human brain with positron emission tomography have begun to address these questions directly. Results from these studies suggest that the cortex may play an important role in mediating the response to cocaine in humans and that persistent changes in dopaminergic systems and cerebral metabolism accompany chronic cocaine abuse. Unfortunately, the nature of human research precludes a systematic evaluation of many of the variables that might affect these neurobiological markers. The lack of control over environmental factors, incomplete and varied drug histories, the high incidence of polydrug abuse, and the presence of comorbid psychopathology can confound the interpretation of data from human studies. Many of these problems, however, can be obviated by the use of a non-human primate model of cocaine self-administration. This model is particularly appropriate because the connectional and chemical anatomy of the dopaminergic mesolimbic system, considered a critical substrate of the reinforcing effects of abused drugs as well as natural reinforcers, is far more complex in the monkey than in rodent and, as such, more closely homologous to that of the human. We propose the use of cocaine self-administration by cynomolgus monkeys to 1) identify the neurobiological changes associated with early and long-term exposure to and abstinence from self-administered cocaine, 2) determine behavioral sequelae of abstinence from cocaine, and 3) relate the neurobiological changes directly to self-administration behavior in the same animal. To accomplish these goals we will: 1) identify the neuroanatomical substrates involved in the early response of cocaine self-administration using the quantitative autoradiographic 2- (14C]deoxyglucose method to measure changes in metabolic activity during the initial exposure of monkeys to cocaine, 2) measure changes in brain metabolism, dopamine transporters and D2 and D3 receptors resulting from long-term cocaine self-administration. Quantitative in vitro receptor autoradiography and in situ hybridization will be used to assess alterations in pre- and postsynaptic elements of the dopaminergic system. 3) identify the changes in brain metabolism, D2 and D3 receptors, and dopamine transporters resulting from cocaine abstinence. Finally, we have designed these experiments to determine behavioral correlates of "craving" which accompanies short-term abstinence from cocaine. The results of the proposed studies will provide a clearer picture of the neurobiological and behavioral basis of cocaine abuse in humans.

Ingested alcohol produces a constellation of discernible subjective effects that are believed to be the result of ethanol's actions on multiple receptor systems at a variety of neuroanatomical sites in the central nervous system. Although the behavioral paradigm of drug discrimination has been used extensively to characterize the neuropharmacological mechanisms that mediate the interoceptive cues produced by ethanol, the neuroanatomical substrates responsible for these cues have received little attention. The goal of these experiments is to identify the network of neural activity that is responsible for the perceptible interoceptive cues that are used by the animal to distinguish ethanol from water in the drug discrimination paradigm. We will first establish the pattern of functional activity in the CNS associated with the discrimination of a low dose (1 g/kg) of ethanol. The purpose of the second set of experiments is to characterize the patterns of activity produced by the administration of higher and lower doses of ethanol that produce varying degrees of ethanol-appropriate responding. Finally, we will determine the neuroanatomical substrates of the effects of drugs with actions at the GABAA receptor complex that reliably produce ethanol-like cues, as well as determine the substrates of the effects of antagonist drugs with actions at the NMDA receptor complex that reliably produce ethanol-like cues. These experiments will provide a more complete understanding of neurobiological basis of the stimulus effects of ethanol responsible for the perceptible interoceptive cues that are used by the animal to distinguish ethanol from water in the drug discrimination paradigm.

The two aims of this core are (1) to provide chronically treated rodents for the projects in this Center; and (2) organize and store tissue from non-human primates as needed by the projects in this Center. Many of the projects described in this program will utilize animal models of chronic drug administration as a means of evaluating the long term consequences of chronic exposures to drugs of abuse. This Core facility will provide animals self-administering cocaine and heroin for the evaluation of various study in Projects I, IV-VI. All routine surgical preparations and training will be provided by the personnel in this Core. Projects I-IV, and VI will require animals chronically treated with novel tropane analogs synthesized in Core C. The present Core will interact considerably with Project IV which will provide in vitro and in vivo testing information regarding the most appropriate dosing, route of administration, and duration of testing of novel tropanes. All routine treatment and testing of animals will be conducted in this Core facility. Finally, Core personnel will be responsible for proper sacrifice, brain collection, and tissue storage of brains from non-human primates utilized in projects in this Center. Records will be maintained for distribution of tissue to various Projects involved in the evaluation of neurobiological markers in non-human primate tissue.

The clinical course of cocaine abuse has been characterized as progressing through a number of temporal stages that advance from initial experimentation through casual use and finally to addiction. On a neurobiological level, this clinical course is paralleled by changes in the response to cocaine with repeated exposure, as well as residual changes in brain function and structure that may persist despite prolonged periods of abstinence from drug use. The studies proposed in the present application will focus on the neuroadaptations that accompany long term exposure to cocaine. We will focus on animals self-administration models, as these models provide valid predictions of human cocaine abuse. Furthermore, differences in the behavioral, pharmacological, and neurochemical responses to cocaine have been shown between self- administered cocaine and cocaine administered non-contingently. In preliminary studies we have observed progressive changes in the patterns of functional activity with continued experience with cocaine self- administration. Structure that form part of the neuroanatomical circuit mediate cocaine self-administration in its initial stages are different from those that appear to be involved later in course of experience with self-administration. Such neuroadaptations may underlie the overall progression of self-administration as it eventually leads to addiction. The overall goals of this project, then are, (1) to extend these findings to examine more closely the evolution of the functional changes associated with cocaine self-administration; (2) to determine the temporal course of adaptations in dopamine and opioid systems that may underlie these changes in functional activity as they develop over time; and (3) to examine the long term effects of novel tropane analogs synthesized in this Center that have been hypothesized as potential medications for cocaine addiction. It is hoped that this approach will provide important insights into the progressive changes that accompany cocaine abuse and provide a basis for developing pharmacological therapies treatments for addiction.

Cocaine addiction continues to be a major public health issue in the United States today. Over time a population of hard core addicts has developed that appear refractory to treatment. In part the development of effective therapies has bene hindered by a lack of understanding of the changes in the response to cocaine with repeated exposure, as well as the residual changes in brain function and structure that can persist despite prolonged periods of abstinence from drug use. The development of non-invasive imaging methods in recent years has made it possible to investigate the neurobiological sequella of cocaine addiction and abstinence directly in humans and relate neurobiological changes to the clinical changes that occur over the course of abstinence. The purpose of experiments proposed in the present application is to investigate the nature and characteristics of the residual changes that persist during abstinence from extended abuse of cocaine using positron emission tomography. In the proposed experiments abstinent cocaine addicts in treatment will be compared to normal controls and current cocaine users in a cross sectional comparison of changes in functional activity as reflected in changes in rates of glucose utilization measured with [18F]fluorodeoxyglucose. A second goal is to determine if the pattern of functional activity seen in abstainers changes with continued abstinence from cocaine. Glucose landscapes obtained early in treatment will be compared to those obtained later in abstinence after sustained treatment. We will compare differences in the abstainers to differences in the scans obtained in normals and users as controls. Although the acute effects of cocaine are relatively brief, persistent alterations in neural function that far outlast the presence of cocaine at its binding sites are also engendered. Recovery from these changes is not likely to be a unitary phenomenon occurring at the same rate in all brain regions. The final goal is to determine if the patterns of functional activity obtained from abstainers following longer periods of abstinence are more like those of normals or cocaine users. It is hoped that this approach will provide important insights into the process of abstinence and provide a basis for developing both pharmacological and behavioral therapies that aid in maintaining abstinence from cocaine.

The effects of ethanol are biphasic with respect to administration time. Positive reinforcement occurs early as blood ethanol levels rise. As these levels fall, the depressant and aversive properties predominate. This time-dependency supports a multi-phasic view of ethanol's effects in the CNS in which ethanol has distinct actions within independent brain systems as a function of time after ethanol administration. Seeking evidence of ethanol-induced changes in disparate neural systems as a function of time, the present proposal will determine whether ethanol affects different neural substrates at different times after ethanol administration and whether these systems adapt to chronic ethanol exposure at different rates. Brain mapping studies are in a unique position to contribute significantly in this regard because they determine levels of activity throughout the brain simultaneously. This laboratory has recently shown that ethanol's effects on functional brain activity in the rat are also time-dependent. Activity was altered immediately after ethanol administration in one set of structures, and activity was altered in a completely different set of structures as blood ethanol levels fell. Therefore, it appears that different neural circuits subserve the effects of ethanol when concentrations are rising and falling. The proposed studies will first extend our previous findings obtained at a single dose to a range of relevant doses in order to establish the conditions of dose and time under which each of these two patterns of brain energy metabolism occur. We also present preliminary data which suggest that functional activity adapts differently to chronic ethanol in distinct sets of brain structures in the rat. Therefore, the present studies will also determine how regional neural activity along the rising and falling phases of the blood ethanol curve change in response to chronic exposure to ethanol. These finding swill contribute to the body of work that supports a concept of tolerance which recognizes that integrated activity among various neural circuits are responsible for the time-dependent effects of ethanol.

DESCRIPTION (provided by applicant): Among the major medical and social problems associated with chronic substance abuse is the manifestation of behavior commonly called addiction. Modern neurobiological research has focused on determining the cellular mechanisms by which the use of drugs of abuse leads to processes responsible for the development of compulsive drug seeking and drug taking, characteristics considered the hallmarks of drug addiction. In order to obtain a fundamental understanding of the adaptations that take place at the level of individual neurons and the neural circuits in which they operate, neurophysiological and molecular biological approaches must be used that can identify how these neurons and neuronal circuits are altered by both acute and chronic exposure to different drugs. This information must then be used to understand how altered activity in these neuronal circuits impacts the generation of specific aspects of addiction, including drug craving, withdrawal, sensitization and relapse. We believe a critical review of the approaches that are used to understand the cellular mechanisms underlying these phenomena will significantly advance our understanding of the addiction process. Further we believe that a venue that offers leading scientists, scientists early in their careers, and students the opportunity to discuss openly their research and hypotheses concerning how these state of the art cellular and molecular approaches can be translated into a better understanding of the human addiction will lead to greater consensus and further collaborative approaches to the study of addiction. Thus, the focus of the 2004 FASEB Summer Research Conference will be Modern Scientific Approaches to Drug Addiction: Relationships with Behavior. The conference will be held July 17-22, 2004 at the Omni in Tucson Arizona. The forum of the Summer Research Conferences provides an informal atmosphere that is conducive to presentation and discussion of up-to-date research findings in an interactive environment. There is only a single symposium or poster session at any given time and all participants dine together at every meal. To ensure an interactive environment, attendees will be limited to 162 participants and 38 faculty. The format includes invited presentations featuring prominent investigators with 15 minutes of discussion for every 30 minutes of formal presentation. There will also be a poster session limited to 50 posters, primarily from young investigators and student trainees.

The clinical course of cocaine abuse has been characterized as progressing though a number of temporal stages that advance from initial experimentation to addiction. This clinical course is paralleled by changes in the neurobiological response to cocaine, as well as residual changes in structure and function that can persist despite long periods of abstinence. The purpose of this project is to expand our understanding of the neuroadaptations accompanying chronic cocaine use, especially those critical for the expression of craving triggered by environmental and internal stimuli associated with drug availability. We will use neuroimaging methods designed to evaluate the entire brain simultaneously in order to evaluate the influence of cocaine exposure across a range of brain targets that may be critical to these behavioral changes. This project makes use of both rodent and non-human primate models of cocaine self-administration. The following questions will be addressed: 1) What is the temporal course of the development of the changes in functional activity that accompany the presentation of cocaine-predictive stimuli as a factor of duration of cocaine exposure, length of abstinence and pattern of drug administration? 2) What is the anatomical distribution of changes in functional activity within the limbic and neo-cortices that accompany the presentation of cocaine-predictive cues after long term self-administration? These studies will employ non-human primates because of the close homology of primate cortex with humans. 3) How do changes in the effects of cocaine-predictive cues on functional activity develop over the course of self-administration experience? These studies will utilize non-invasive imaging with positron emission tomography to assess rates of glucose utilization repeatedly in the same animal. This approach will permit the establishment of the temporal course of functional changes in the same animal at a number of time points. Because we will be using a within subjects design, it will also be possible to examine the time course in each individual animal, thus permitting an evaluation of individual differences in the response to chronic cocaine exposure. In short, the goal of these studies is to characterize the sites of changes in functional activity that result from chronic cocaine exposure investigating the factors important for the initiation and progression of these changes over the course of cocaine self-administration experience. These data will provide a clearer picture of the neuroadaptations that can influence behavior days, weeks or even years after abstinence.

Marijuana is the most widely used illicit drug in the United States today, with over 5 million individuals reports use within the last 20 days. Decision making is required for behaviors ranging from simple motor movements to complex reasoning about future consequences. A recent report from our lab has shown that marijuana users have impaired decision making as measured by the Iowa Gambling Task, a laboratory- based decision making task. Marijuana users, as compared to controls, made significantly more risky choices. Furthermore, mathematical modeling of these data has suggested that marijuana users perform poorly because they have deficient cognitive and response style processes. The overall goal of this application, then, is to isolate the specific processes underlying the poor performance of marijuana users by investigating performance on tasks specific to each of these two processes. In the proposed studies recent heavy marijuana users will be compared to non-using controls on performance of an N-back task, a test of working memory and a GO/NOGO task, a test of impulsive response style, as well as the Gambling Task. In addition, functional magnetic resonance imaging (fMRI) will be used to examine brain activity during the performance of these three tasks. Discriminant analyses will be used to distinguish the relationship among performance measures in an effort to identify the root causes of deficient decision-making in this population. We will also relate patterns of brain activity to performance variables and to each other to look for common elements across patterns. This will provide information about the underlying neural processes associated with, chronic marijuana use. Because marijuana is often thought to be less risky than other abused drugs, its potential deleterious effects are often ignored or unrecognized. Chronic marijuana use is therefore a major national public health concern. The present studies seek to identify the nature and sources of deficient decision-making by marijuana users.

[unreadable] DESCRIPTION (provided by applicant): The periods of adolescence and early adulthood are times of risk for the development of addiction and substance abuse disorders. Although there are many risk factors that may increase vulnerability, including family history, genetic background, psychiatric and behavioral disorders, and peer pressure, one important factor is early exposure to drugs during childhood. This has raised concerns about the use of stimulant medications for childhood psychiatric disorders such as attention deficit hyperactivity disorder (ADHD). Most of the studies conducted in children and adults with ADHD have suggested that medication with methylphenidate or amphetamine has either no effect or can be protective from substance abuse disorders. However, it is impossible to distinguish between the effects of the stimulants and ADHD itself. Given that these stimulants can produce dramatic neuroadaptations in the dopamine system and disruptions of dopamine systems may increase vulnerability to drug abuse, the question of long-term adverse consequences of stimulant medication still remains. The overall purpose of this application is to address this question in a non-human primate model. Juvenile rhesus monkeys (approximately 20 mos at the start of the study) will be exposed to oral doses of methylphenidate or amphetamine or placebo for one year. Dopamine function as assessed with positron emission tomography, brain development assessed with magnetic resonance imaging, and markers of physical growth and social development will be measured before treatment commences, at the end of treatment and 3 months after cessation of the medication regimen. Finally, we will assess the reinforcing efficacy of the psychostimulant cocaine once monkeys enter adolescence. These studies are not intended to evaluate all of the potential consequences of stimulant medication in childhood for the treatment of ADHD, but to answer the question of whether stimulant exposure can predispose adolescents to the development of substance abuse disorders. [unreadable] [unreadable]

Despite significant efforts cocaine abuse remains a continuing public health problem. Chronic cocaine use is accompanied by neuroadaptations in multiple neurotransmitter systems, as well as enduring changes in brain functional activity. To date there are no FDA approved medications for treatment of cocaine dependence. Drug development efforts are hampered by the lack of understanding of the neurobiological basis of potential pharmacotherapeutic strategies. The goal of these studies proposed is to characterize at a systems level the neurobiological effects of potential treatment drugs that have shown positive signals in current clinical trials, drugs approved for use In humans being considered for use in treatment;and mechanistic drug treatments for which preliminary animal studies suggest may be useful in reducing cocaine reinforcement based on their mechanisms of action. The convergence of Information from these different strategies will provide critical Information about the neuropharmacological mechanism of effective treatment and guide future drug development. Aim 1 will evaluate the consequences of chronic administration of candidate medications and then assess the neurobiological effects of these medications in rodent models of chronic cocaine self-administration in neurochemical systems as established in Project 1 We will measure changes in the function of dopamine systems using microdialysis in freely moving rats and voltammetry in brain slices and assess changes in functional brain activity with the 2-deoxyglucose method and the expression of immediate early genes consequent to chronic treatment with candidate medications. Aim 2 will make use of established nonhuman primate models of cocaine self-administration to evaluate the consequences of these potential pharmacotherapies on brain transmitter systems and to characterize the sites of changes in functional activity accompanying responses to cocaine-associated cues and cognitive processes as established in Project 1 It is only through a systems level analysis with clinically relevant models of substance abuse as proposed in this application that a greater understanding of the neurobiological basis of treatment can emerge. Thus, the systems approach of Project 2 provides a bridge between behavioral evaluations in Project 1 and the cellular approaches in Project 3.

Project 2 Summary Functional Consequences of Putative Pharmacotherapies for Cocaine Dependence in Animal Models of Cocaine Exposure Drs. Sara Jones/Linda Porrino, co-PI's; Drs. Sam Deadwyler and Mark Ferris, co-I's  Cocaine abuse is a significant public health problem, but attempts to develop effective treatments for cocaine abuse and dependence have met with only limited success. One promising development in the clinic has been the use of combination medications to treat the broad range of symptoms and neuroadaptations that result from cocaine exposure. In the prior funding period, the Center found that stimulant drugs, specifically amphetamines, were among the more efficacious strategies for reducing cocaine reinforcement. Building on this foundation, new preliminary data, and advice from the Center's clinical partners we have chosen to examine the stimulant releaser phenmetrazine and its oral pro-drug, phendimetrazine, which have much lower abuse liability to address the dysregulation of dopamine function that is characteristic of cocaine abuse. Another hallmark characteristic of cocaine dependence is reduced prefrontal cortical function and accompanying deficits in behavioral control and cognition. Because multiple transmitter systems are involved in regulating prefrontal cortical function and glutamatergic output from this region, drugs that act on specific prefrontal circuits have been selected for testing as combination drug candidates with phenmetrazine. These drug combinations will be chosen in consultation with other Center Projects and our clinical partners. In the previous funding cycle, we established neurobiological ?signatures? of functional activity, dopamine dynamics, cognitive function and cortical processing that relate to cocaine self-administration and its pharmacological manipulation. This Project will use these data to form the foundation of studies proposed here to examine the neurobiological consequences of chronic phenmetrazine and combination drug therapies in rodent and nonhuman primate models of cocaine use and abuse. Specific Aim 1 will use rats to measure changes in the function of the dopamine system and identify brain regions with altered metabolic activity after cocaine self- administration and chronic treatment with combinations of candidate medications. Specific Aim 2A will use nonhuman primates to characterize the effects of cocaine cues on PET measures of cerebral metabolism after chronic cocaine exposure and treatment with combination medications. Specific Aim 2B will evaluate the effects of chronic cocaine exposure with combination medications on cerebral metabolism during the performance of a cognitive task. In addition, electrophysiological recordings of prefrontal cortex will be used to evaluate changes in neural circuitry induced by combination medications that alleviate cocaine addiction.