Therese A. Kosten - US grants

DESCRIPTION: (Applicant's Abstract) Among heroin addicts, alcohol abuse is a significant problem. While alcohol use is due, in part, to its reinforcing effects, this dual addiction may reflect additional factors, as suggested by recent research. Ethanol blocks the NMDA-glutamate activated ion channel, a system implicated in many neural plasticity phenomena, including responses associated with chronic drug exposure. The development of analgesic tolerance and dependence to morphine and locomotor sensitization to psychostimulants is attenuated by dizocilpine, an uncompetitive NMDA antagonist. Given that ethanol may mimic dizocilpine, it too, may attenuate plasticity effects of chronic drug use. Indeed, our preliminary data confirm that ethanol, like dizocilpine, attenuates morphine dependence. The proposed studies would extend that finding to include several behavioral plasticity phenomena associated with chronic morphine exposure, including: 1) dependence, as evaluated by naloxone-precipitated withdrawal aversion; 2) locomotor sensitization and; 3) tolerance to the place conditioning effects of morphine after chronic exposure. The ability of dizocilpine and ethanol to attenuate morphine dependence may occur via their NMDA antagonist effects, which will be assessed in another study proposed herein. Specifically, we will determine whether the ability of dizocilpine or ethanol to attenuate morphine dependence can be blocked by NMDA treatment. Finally, dizocilpine, and perhaps ethanol, may enhance the behavioral effects of morphine. Indeed, we find that dizocilpine enhances the ability of morphine to lower the threshold for brain stimulation reward. Thus, a final set of studies will investigate further whether dizocilpine and ethanol enhance the locomotor sensitizing, discriminative stimulus, and place conditioning effects of morphine. All studies will address these questions by assessing shifts in morphine dose-response functions. These preclinical studies may provide information indicating that the pharmacological interactions of these two drugs enhance their abuse potentials which may have implications for understanding and treating dual addiction to heroin and alcohol.

Recent research suggests a role for the hypothalamic-pituitary-adrenal (HPA) axis in the behavioral effects of cocaine. Cocaine induces glucocorticoid release (e.g., corticosterone, ACTH) probably due to corticotropin releasing factor (CRF). In general, treatments that increase levels of these hormones enhance some behavioral effects of cocaine, whereas treatments that decrease levels of these hormones attenuate some of these effects. This includes stressor exposure that activates the HPA axis and amplifies the behavioral effects of cocaine. And, greater behavioral responsivity to cocaine has been related to inherently high HPA axis hormone levels. Inherent differences in HPA axis function exist between two inbred strains, lewis and Fischer 344 (F344) rats, which also differ in their behavioral and biochemical responses to psychoactive drugs. Lewis rats, compared to F344 rats, exhibit enhanced sensitivity to and preference for cocaine. These strains also differ in several biochemical characteristics of the mesolimbic dopamine system, a neural area associated with drug responses. Paradoxically, Lewis rats have blunted HPA hormonal activity and impaired autoimmune responses. That HPA axis hormones interact with the immune system (e.g., ACTH induces release of some cytokines) may have important implications for the relationship of immunological diseases, such as HIV infection, and cocaine abuse. This grant will compare how various manipulations of the HPA axis (e.g., glucocorticoid administration adrenalectomy, CRF antiserum and antagonist administration, stress exposures) affect the neurobehavioral responses to cocaine in Lewis and F344 rats; these strains provide models both to study interactions of the neuroendocrine and immune systems and to study vulnerability to drug abuse. Behavioral measures will include locomotor activity, place conditioning, drug discrimination, and self-administration. Biochemical measures will include many signal transduction proteins (e.g, tyrosine hydroxylase, protein kinase A) regulated specifically in VTA/NAcc by chronic drug or stress exposure. In addition, levels of ACTH-related cytokines will be assessed. These studies may provide insight into possible differing etiologies and treatment approaches for cocaine abuse.

DESCRIPTION (provided by applicant): The long-term goals of this research project are to elucidate the molecular and cellular mechanisms for neuroadaptations to ethanol. Previous studies have identified two new Drosophila mutants with a heightened sensitivity and impaired tolerance to ethanol. Preliminary spatial expression studies of one mutant, named homer, have suggested that the normal gene's function is sufficient in GABAergic neurons that innervate the ellipsoid body for normal behavioral responses to ethanol. These studies will be confirmed and extended. In addition, the directed expression of RNAi constructs and dominant negatives will be used to define where Corner expression is required in the adult brain for wild type behavioral responses to ethanol. Newly developed techniques that provide for experimenter control over transgene expression in time and space will be used to ascertain whether homer is required during development or whether it is required physiologically in the adult fly. Similar time and space expression studies using a normal transgene of the second mutant, named yps, will be performed to ascertain whether this gene's function is required in the same set of neurons and at the same time as homer for normal ethanol responses. RNA from neurons that require homer and/or yps will be isolated using newly developed affinity techniques and used to probe microarrays to define the changes in gene expression that occur with ethanol exposure in this specific set of neurons. The observed changes in gene expression with ethanol exposure will be used to predict which genes are functionally involved in behavioral responses to ethanol, and mutants in these genes will be assayed to further define the molecular genetic requirements for normal ethanol sensitivity and tolerance. These studies will further our understanding of the genetic basis for ethanol sensitivity and tolerance, important parameters for susceptibility to alcoholism.

[unreadable] DESCRIPTION (provided by applicant): The long-term goals of this research project are to elucidate the molecular and cellular mechanisms for neuroadaptations to ethanol. Previous studies have identified two new Drosophila mutants with a heightened sensitivity and impaired tolerance to ethanol. Preliminary spatial expression studies of one mutant, named homer, have suggested that the normal gene's function is sufficient in GABAergic neurons that innervate the ellipsoid body for normal behavioral responses to ethanol. These studies will be confirmed and extended. In addition, the directed expression of RNAi constructs and dominant negatives will be used to define where Corner expression is required in the adult brain for wild type behavioral responses to ethanol. Newly developed techniques that provide for experimenter control over transgene expression in time and space will be used to ascertain whether homer is required during development or whether it is required physiologically in the adult fly. Similar time and space expression studies using a normal transgene of the second mutant, named yps, will be performed to ascertain whether this gene's function is required in the same set of neurons and at the same time as homer for normal ethanol responses. RNA from neurons that require homer and/or yps will be isolated using newly developed affinity techniques and used to probe microarrays to define the changes in gene expression that occur with ethanol exposure in this specific set of neurons. [unreadable] [unreadable] The observed changes in gene expression with ethanol exposure will be used to predict which genes are functionally involved in behavioral responses to ethanol, and mutants in these genes will be assayed to further define the molecular genetic requirements for normal ethanol sensitivity and tolerance. These studies will further our understanding of the genetic basis for ethanol sensitivity and tolerance, important parameters for susceptibility to alcoholism. [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Understanding sex differences in the initiation to addiction are important goals as evidenced by the FOA (PAS-07-382) to which this exploratory grant is addressed. We propose a novel yet hypothesis-based approach to examine sex differences in stress responsivity and addiction using established animal procedures. Stress responsivity relates to acquisition of cocaine self-administration, an animal model of vulnerability to addiction. Stress responsivity shows sex differences but reports on self-administration are conflicting. Links between maternal care and stress responsivity of offspring are proposed; greater care relates to lower stress responsivity of adults. Maternal care differs by pup sex; male pups receive more care than female pups. Adult males show lower stress responsivity than females consistent with the link of maternal care with stress responsivity. We hypothesize that sex-dependent maternal care influences sex differences in stress responsivity and cocaine self-administration in the adult. We will test this by manipulating maternal care via altering litter gender composition (LGC; single- vs mixed-sex litters) because pups of single-sex litters receive more care than pups of mixed-sex litters. LGC influences stress responsivity in infant mice and juvenile and maternal behaviors in rats and mice. We predict both male and female adult rats of single-sex litters will show lower stress responsivity than offspring of mixed-sex litters. In Specific Aim 1, we will confirm prior studies demonstrating sex-specific effects of maternal care. We will measure stress hormone levels after stress exposures and assess glucocorticoid feedback sensitivity. We predict the following effects of LGC on stress responsivity: mixed females>single females >=mixed males>single males. The relationship between stress responsivity and cocaine self-administration is complex and may be non-linear; both low and high stress responsivity may associate with low responding. Thus, we predict LGC will attenuate acquisition of cocaine self-administration in mixed females and single males and, overall, result in an inverted U-shaped function of stress responsivity to cocaine self-administration. Studies in Specific Aim 2 will test the effects of LGC on acquisition of cocaine self-administration with a parallel study on acquisition of food responding. Behavioral sensitivity to foot shock will also be investigated. Data will inform on contributions of stress responsivity to sex differences in vulnerability to addiction. PUBLIC HEALTH RELEVANCE: The goal of this research program is to achieve a better understanding of sex differences in stress responsivity and vulnerability to addiction using animal models. Studies in this proposal will test the hypothesis that these sex differences are due to sex-dependent differences in maternal care received suggestive of epigenetic origins of the sex differences in stress and drug responses in the adult. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): This application proposes a core integral to the INIA-West Consortium tasked to identify target medications to treat alcoholism. Agents will be identified based on information obtained from projects within INIA-West. The agents will be examined to determine if they alter behaviors reflective of the various aspects of alcoholism including binge-intoxication, negative affect, and preoccupation-anticipation in a systematic manner using established behavioral methods with rats. Tests are conducted in an orderly manner with clearly defined decision points for continuation or cessation of studies with an agent. An agent's ability to alter behaviors indicative of binge-intoxication is examined using maintenance of operant self-administration of alcohol under progressive ratio schedules and promising results followed by place conditioning and 2-bottle preference procedures. Alleviation of negative affect is assessed by measuring withdrawal signs and anxiety- and depressive-like behaviors with elevated plus maze and forced swim tests. Preoccupation-anticipation ("craving") is assessed with drug/cue-induced reinstatement of extinguished operant responding, conditioned approach, and sign-tracking. This set of "craving" studies is a focal point of the grant given the importance of relapse prevention in alcoholism treatment and a reason rats are used as these procedures are more difficult to establish with mice. Further, because excessive alcohol can cause cognitive deficits that would likely interfere with psychological treatments (which are often combined with pharmacological treatments), we will also assess whether target agents alter cognitive function using standard learning and memory tasks (e.g., fear conditioning, object recognition, delayed alternation). Studies will be conducted in rats that have been chronically exposed to alcohol vapors. This project interacts closely with the Roberts and Bell projects to confirm or extend findings allowing greater confidence in results obtained. Finally, in collaboration with other projects and cores and using molecular genetic and neuropharmacological approaches, we will confirm the neurobiological effects of the target agents to alter chronic alcohol effects. PUBLIC HEALTH RELEVANCE: The goal of this research program is to establish a behavioral testing core for the INIA-West Consortium aimed at testing potential pharmacotherapeutic agents for alcoholism. The main focus of this core is to conduct tests reflective of "craving" although other aspects of alcoholism (intoxication, negative affect) will be addressed and results compared to those of the Bell and Roberts cores.