Jill B. Becker - US grants

Depletion of brain dopamine (DA) in rats produces a syndrome of aphagia, adipsia, bradykinesia, and profound sensorimotor neglect. This bradykinesia and sensorimotor neglect is not due to a primary sensory or motor deficit, but has been characterized as a deficit in sensory-motor integration. These symptoms are very similar to those seen in Parkinson's Disease, which is thought to be due to a loss of DA-containing neurons in the substantia nigra. Although rats with bilateral DA depletion have provided many insights into the function of brain DA neurons, they are difficult to maintain, requiring extensive post-operative care. However, rats with unilateral nigrostriatal DA depletion have provided a very useful animal model of Parkinson's Disease. These animals neglect stimuli presented to the contralateral body surface or space, and when treated with DA-mimetic drugs display a highly quantifiable behavioral asymmetry known as rotational (circling) behavior. Recently, it has been shown that grafts of fetal substantia nigra or adrenal medulla tissue placed in or near the denervated striatum can at least partially reverse these behavioral asymmetries. The evidence available to date suggests that these grafts alleviate the symptoms of DA depletion by releasing catecholamines, but this hypothesis has never been directly tested. In this application we propose a series of experiments to do so. In the first series of experiments we propose to develop a push-pull perfusion technique to measure the efflux of catecholamine metabolites into the lateral ventricle as an index of catecholamine release. Next, we will compare the ability of fetal substantia nigra, adrenal medulla or fetal tectal tissue grafts placed into the lateral ventricle to release catecholamines and/or catecholamine metabolites into the lateral ventricle, over time following the transplant. Thirdly, we will use a series of pharmacological manipulations to determine: (1) if there is any relation between the ability of catecholamine-rich tissue grafts to release catecholamines and their ability to attenuate the rotational behavior imbalance produced by unilateral DA depletion; and (2) whether any of the normal mechanisms governing catecholamine release are operative in tissue grafts.

Females of many species, including humans, tend to have lower thresholds for sensory stimuli and can perform motor tasks more rapidly than males. Moreover, differences in sensorimotor function normally occur during the estrous cycle or menstrual cycle and administration of exogenous gonadal steroid hormones can mimic these natural changes. Dr. Becker has evidence to suggest that estrogen enhances sensorimotor responsiveness by having direct effects on the neurons of the basal ganglia that use dopamine as the neurotransmitter. She will examine this steroid-neurotransmitter relationship by analyzing both presynaptic and postsynaptic effects of estrogen on the dopamine system. By comparing the effects of estrogen on dopamine release and receptor activity in both males and females, Dr. Becker will determine whether the known sex differences in sensorimotor performance is related to biochemical differences. Her experiments not only enhance our understanding of the relationship between hormones and neurotransmitters but also how these processes modulate basal ganglia function. Since the basal ganglia of the brain is involved in a number of clinical disorders, including Parkinson's Disease and Huntington's Disease, these results have important implications for our understanding and treatment of these debilitating disorders and other related movement disorders.

Depletion of brain dopamine (DA) in rats produces a syndrome of aphagia, adipsia, bradykinesia and profound sensorimotor neglect. This bradykinesia and sensorimotor neglect is not due to a primary sensory or motor deficit, but has been characterized as a deficit in sensory-motor integration. These symptoms are very similar to those seen in Parkinson's Disease, which is thought to be due to a loss of DA-containing neurons in the substantia nigra. Although rats with bilateral DA depletion have provided many insights into the function of brain DA neurons, they are difficult to maintain, requiring extensive post-operative care. However, rats with unilateral nigrostriatal DA depletion have provided a very useful animal model of Parkinson's Disease. These animals neglect stimuli presented to the contralateral body surface or space, and when treated with DA-mimetic drugs display a highly quantifiable behavioral asymmetry known as rotational (circling) behavior. Recently, it has been shown that grafts of fetal substantia nigra or adrenal medulla tissue placed in or near the denervated striatum can at least partially reverse these behavioral asymmetries. The evidence available to date suggests that these grafts alleviate the symptoms of DA depletion by releasing catecholamines, but this hypothesis has never been directly tested. In this application we propose a series of experiments to do so. In the first series of experiments we propose to develop a push-pull perfusion technique to measure the efflux of catecholamine metabolites into the lateral ventricles as an index of catecholamine release. Next, we will compare the ability of fetal substantia nigra, adrenal medulla or fetal tectal tissue grafts placed into the lateral ventricle to release catecholamines and/or catecholamine metabolites into the lateral ventricle, over time following the transplant. Thirdly, we will use a series of pharmacological manipulations to determine: (1) if there is any relation between the ability of catecholamine-rich tissue grafts to release catecholamines and their ability to attenuate the rotational behavior imbalance produced by unilateral DA depletion; and (2) whether any of the normal mechanisms governing catecholamine release are operative in tissue grafts.

Lesion of the nigrostriatal dopamine system in rats produce a syndrome of aphasia, adipsia, bradykinesia, and profound sensorimotor neglect, symptoms similar to those seen if Parkinson's Disease. Grafts of dopamine-rich tissue in or near the striatum have been reported to alleviate many of the behavioral deficits produced by the destruction of nigrostriatal dopamine neurons. Experiments will investigate the neurochemical processes associated with behavioral recovery of function induced by grafts of adrenal medulla or fetal substantia nigra tissue in animals with nigrostriatal dopamine depletions. It is hypothesized that dopamine released from adrenal medulla grafts gins assess to the adjacent striatum via a compromised blood-brain-barrier to mediate the behavioral effects of these grafts. In contrast grafts of fetal tissue are thought to induce behavioral recovery by the formation of synaptic contacts. Experiments are proposed to test these hypotheses. with microdialysis in freely moving rats, experiments with adrenal medulla grafts will examine whether the blood-brain-barrier to dopamine is compromised and if so. whether this is correlated with the behavioral and neurochemical efficacy of these grafts. Experiments will then attempt to dissociate dopamine release them graft vs host of prier to determine whether there are changes in the activity of host dopaminergicneurons (e.g. neurochemical corelates of sprouting). In animals with bilateral dopamine depletion. The effect of unilateral adrenal medulla grafts on bilateral recovery of behavioral and neurochemical function will be tested. Finally, we will examine whether changes in host cholinergic activity is associated with behavioral recovery in animals with adrenal medulla grafts. The behavioral and neurochemical effects of fetal nigra grafts will be investigated using microdialysis to study the relations between graft-associated recovery of function and changes in the neurochemical function of grafted and host neurons. The relations between dopamine and acetylcholine in the straitum of animals with fetal nignal grafts amy reveal the extent of functional synaptic innervation by fetal nignal graft that occurs. Since it s well known that there is a delicate balance between dopamine and aceryicholine in the striatum, these relations may be of fundamental importance for behavioral recovery of function. Grafts of both adrenal medulla and fetal nigra tissue have already been applied clinically for the treatment of patients with severe Parkinson's Disease. The reports of the success of these grafts remains mixed. Answers about the neural mechanisms that mediate behavioral recovery of functions in animals with adrenal medulla and fetal grafts may be of fundamental importance for improving graft efficacy. The experiments proposed are a first step towards achieving this goal.

Lesions of the nigrostriatal dopamine system in rats produce a syndrome of aphasia, adipsia, bradyknesia, and profound sensorimotor neglect, symptoms similar to those seen in Parkinson's Disease. In the hemi-Parkinsonian rat, stimulation with drugs that induce dopamine release (e.g., amphetamine) or act as agonists at dopamine receptor (e.g., apomorphine) induce behavioral asymmetries, and in particular rotational behavior. Substantia nigra anlage or adrenal medulla tissue grafted into or adjacent to the dopamine-denervated striatum have been shown to alleviate many of the behavioral deficits associated with unilateral nigrostriatal dopamine denervation. Experiments are proposed using behavioral, neurochemical, and morphological methods to further delineate the mechanisms mediating recovery of function after grafts of adrenal medulla or substantia nigra anlage. Our results suggest that these types of grafts produce their effects on the dopamine-denervated striatum by different mechanisms, that multiple mechanisms are involved, and that the mechanism(s) may vary with the type of cell that is transplanted into the brain. For example, if animals with adrenal medulla grafts are tested for rotational behavior with both amphetamine and apomorphine some animals have decreased amphetamine-induced turning and others have decreased apomorphineinduced turning, fewer than 10% have both. With grafts of substantia nigra anlage individual differences in behavior are seen in the response to amphetamine. Some animals with these grafts exhibit less amphetamine-induced turning, others reverse their direction of turning. The relationship between behavioral recovery and neurochemical indices of neurological function following these grafts is the topic of the research proposed here. Defining the events necessary for behavioral recovery after these grafts will illuminate ways in which to improve their survival and behavioral efficacy. By studying individual differences in graft effects, rather than studying only group effects, those mechanisms and procedures most likely to promote recovery of function in all individuals can be discerned. In the experiments proposed we take the next step towards defining the neurochemical processes mediating individual differences in behavioral recovery after transplantation of dopaminergic tissue into brain. The neural processes mediating recovery of function in this animal model of Parkinson's Disease are not necessarily unique. Thus, the results of these experiments may also contribute to the development of improved therapies for other neurological disorders, including Alzheimer's Disease and Huntington's Disease.

In female rats, the gonadal hormones estrogen and progesterone modulate activity of the neurotransmitter, dopamine (DA), in the brain. Experiments in this laboratory have been directed at defining the mechanisms mediating the effect of estrogen in the brain, as well as attempting to determine the functional role of this phenomena in the natural behavior of the rat. With the latter in mind, we find that DA in one particular area of the brain, the striatum, is important for specific aspects of the female rat reproductive behavior. The mechanism(s) mediating the effects of the gonadal hormones on the striatum appears to be different from those mediating the effects of estrogen and progesterone at intracellular (traditional) estrogen receptors. Research from my laboratory has repeatedly demonstrated that estrogen acts in the striatum through a novel mechanism. There are two key questions about the role of gonadal hormones in the modulation of DA activity in the female rat that the experiments in this proposal will address: 1) What are the mechanism(s) mediating the effects of estrogen on the striatum?; and 2) What role(s) of the striatum, and of DA release, in reproductive behavior in the female rat?
The involvement of the gonadal steroid hormones in the modulation of striatal DA activity is important for our understanding of the basic processes of neuroendocrinology as well as our understanding of the functions of the basal ganglia. Identifying novel mechanisms through which steroid hormones act in the brain has important implications for our understanding of where, how, and when these hormones affect the brain activity and behavior. Finally, these experiments will help us to understand how these hormones modulate behavior in the female rat.

DESCRIPTION (provided by applicant): Women begin using cocaine, enter treatment at earlier ages than men, and have more severe cocaine use at intake than men. Thus, women progress from initial use to dependence faster than men do. This "telescoping" effect reflects a briefer time course for the development of medical consequences and behavioral/psychological factors characteristic of a dependence disorder. The studies proposed are a fundamentally important first step towards understanding structure-function relations in the induction and expression of drug-taking behavior and the long-term consequences of this behavior in both males and females. In this proposal we seek to identify the hormonal and developmental events that produce a sexually dimorphic ascending dopamine system that results in sex differences in drug abuse liability, and to identify some of the associated neural processes that mediate these sex differences. There are two times during development of the brain when hormones can influence its organization. In the rat these occur during the peri-natal period and again during the peri-pubertal period. Experiments are proposed to test the hypothesis that the enhanced vulnerability of females for cocaine abuse is dependent on the lack of exposure to gonadal hormones during the critical perinatal period, as well as subsequent exposure to ovarian hormones during the peripubertal period. Self-administration of cocaine will be used as the primary outcome measure. Acquisition of drug taking behavior during adolescence in humans is a strong predictor of drug abuse problems as an adult. We hypothesize that onset of hormone exposure during the peri-pubertal period contributes to increased vulnerability for the reinforcing and/or long-term consequences of cocaine treatment in both males and females. We will determine whether adolescence is a period of enhanced vulnerability for female vs. male rats to self-administer cocaine. Alternatively, it is possible that adolescents aren't more vulnerable to the addictive properties of the psychomotor stimulants, but that the long-term consequences of exposure to these drugs during adolescence result in increased susceptibility as an adult, this possibility will be examined as well. Finally, the neural basis of the organizational and developmental influences on sex differences in the response to cocaine will be examined by looking at dopamine in dialysate from striatum and nucleus accumbens. These experiments are a first step towards exploring the extent that sex differences in vulnerability for cocaine abuse impacts the striatum and nucleus accumbens. Women are more vulnerable to becoming addicted to cocaine than are men. The experiments proposed will investigate the neurodevelopmental processes that contribute to this gender difference in drug abuse using a preclinical model. The long-term goal of this project is to develop better intervention and treatment protocols for both men and women based on an improved understanding of neural basis of vulnerability to addiction.

DESCRIPTION (provided by applicant): The classical receptor for estradiol, ERalpha in addition to its genome-activating properties, is also found within the extracellular membrane where it induces rapid responses to estradiol(E). These receptors are now referred to as membrane ERalpha (mERalpha). It has been demonstrated that E acting extracellularly on mERalpha can rapidly initiate a variety of signal transduction cascades. Brain regions known to be sensitive to the rapid effects of E include the striatum and nucleus accumbens (NAcc). Considerable research has demonstrated that ovarian hormones rapidly activate behavioral and neurochemical indices of dopamine activity in the striatum of female but not male rats. Electrophysiological experiments have shown that E rapidly inhibits the calcium current mediated by L-type calcium channels in medium spiny GABA neurons. Thus, we hypothesize that the enhancement of DA release after E treatment is due to decreased GABA release resulting in a release of inhibition at GABA (B) receptors on presynaptic DA terminals. The experiments proposed will investigate the mechanisms mediating the effects of E in the striatum and nucleus accumbens (NAcc). Specific Aim 1 will test the hypothesis that the enhanced DA release seen after estradiol treatment is due to estradiol, acting on neurons in the striatum to block current mediated by L-type calcium channels. This is hypothesized to produce decreased GABA release and thereby decrease activity at GABA (B) receptors on presynaptic DA terminals. Specific Aim 2 will test the hypothesis that mERa mediates the response to estradiol in the striatum and NAcc. Experiments will use an adeno-associated viral vector (AAV) that expresses the ERa transgene, a transgene that is a dominant negative for the mERalpha, or a control vector to determine whether the behavioral and neurochemical effects of estradiol in the striatum are mediated by mERalpha. The mechanisms through which E acts in the brain and body are important to understand in order to improve our treatment and decrease risks for hormone replacement therapy, breast cancer, and ovarian cancer. It may also be important for our understanding and treatment of a number of neurological disorders including stroke, Alzheimer's disease and Parkinson's disease where estradiol may be neuroprotective.

DESCRIPTION (provided by applicant): Experiments are proposed to investigate the interaction between two risk factors for drug abuse: prenatal stress and being female. It is hypothesized that prenatal stress alters the neural systems that respond to novel situations differentially in males vs. females, but the consequences for both sexes is an enhanced response to cocaine which increases vulnerability for drug taking behavior. Prenatal stress exposes the developing organism to increased levels of glucocorticoids at a time during which critical growth is taking place so there are profound effects on the development of the nervous system and as a consequence the physiology and behavior of the adult offspring. Some of the consequences of prenatal stress include dysfunction of the stress axis, learning disabilities, depression, psychopathology and potentially an increased propensity to develop drug abuse. There are sex differences in drug abuse for many drugs of abuse, and even though there are more men with substance abuse disorders, the onset of addiction to cocaine is more rapid in women than in men. Women begin using cocaine at an earlier age, enter treatment at earlier ages and have developed more severe cocaine dependence at intake than men. In rats, female rats exhibit an enhanced behavioral sensitization to cocaine, they acquire cocaine self-administration more rapidly and at lower doses, and females exhibit greater motivation to take cocaine than do male rats. In results from pilot experiments we find in male rats that prenatal stress enhances behavioral sensitization following repeated cocaine, and acquisition of cocaine self-administration. In females, results of pilot experiments indicate that prenatal stress enhances the locomotor response to novelty, the acute response to cocaine, behavioral sensitization to cocaine, and the amount of cocaine taken on certain days of the estrous cycle. Thus, there is also increased risk for females after prenatal stress. Experiments proposed will test the hypothesis that prenatal stress increases vulnerability of males and females for the behavioral response to cocaine and cocaine self-administration via altered stress system-related gene expression and changes in dopamine function in the nucleus accumbens and striatum. The mechanisms mediating the effects of prenatal stress are hypothesized to be different for males vs. females, but the consequences for both sexes is an enhanced response to cocaine which increases vulnerability for drug taking behavior. Importantly, many of the effects of prenatal stress can be reversed by cross-fostering to non- stressed dams. Experiments will also investigate the extent that maternal behavior can ameliorate the effects of prenatal stress on stress system-related gene expression, change dopamine function in the nucleus accumbens and striatum and on drug taking behavior. PUBLIC HEALTH RELEVANCE: Why do some individuals start taking drugs of abuse? Experiments proposed will investigate what goes wrong in the brains of males and females as consequence of prenatal stress that may lead to addiction, and whether it is possible to compensate for these effects by changes in maternal behavior. Results from these experiments will have implications for treatment and prevention of drug abuse using non-pharmacological interventions.

DESCRIPTION (provided by applicant): This application is a request for partial funding to support the fourth annual meeting of the Organization for the Study of Sex Differences (OSSD), to be held June 3 - 5, 2010 in Ann Arbor, MI. OSSD is a scientific membership society that was established in 2006, in partnership with the Society for Women's Health Research. The mission of OSSD is to enhance the knowledge of the biological basis of sex/gender differences in health and disease by facilitating interdisciplinary communication and collaboration among scientists and clinicians from diverse scientific and professional backgrounds. The OSSD annual meeting provides a forum for scientists to explore aspects of sex differences research at the genetic, molecular, cellular, organ, and system levels in humans and model systems. The annual meeting consists of a Keynote opening lecture, a closing Capstone lecture, seven independent symposia, and a New Investigator Symposium. The symposia topics for the 2010 meeting include Evolution and the Origins of Sex Differences in Mortality;Genetic and Environmental Determinants of Parent of Origin Specific Genomic Imprinting;Pain, its Treatment, and the Influence of Sex;Antenatal Corticoids: Sex-based Differences in Respiratory System Ontogeny and Function;Sexually Differentiated Responses and Estrogen Receptors;Sex Differences in Neuroplasticity during Development and in Adults;and Sex Differences in Oxidative Stress, Non-Reproductive Cancers, and Longevity. The OSSD Programs Committee selected the symposia topics from among proposals submitted by the OSSD membership based on scientific merit, relevance of the subject matter, inclusion of basic and clinical speakers, prior topics covered in recent OSSD programs, and suggestions from the survey conducted after the previous meeting. In addition to the keynote lectures and symposia, there are two afternoon poster sessions scheduled, which will be arranged around topics covered in these symposia and will highlight the work of new investigators and trainees. The size (~150 people) and the organization of this meeting provide an excellent opportunity for networking opportunities and interactive discussions. Based on attendance at the previous three annual meetings we expect approximately two thirds of the participants to be established investigators and a third to be new investigators. Funds are requested to support the travel and lodging costs for the Keynote and Capstone speakers, registration fees for invited speakers, audiovisual equipment and meeting room rental costs, and support for junior investigator travel and awards. The annual meeting program, including speaker and poster abstracts will be made freely available on the OSSD website (www.ossdweb.org). We will partner with the University of Michigan to organize this event and will also request support from the National Science Foundation, as well as pharmaceutical and biotechnology companies and from private foundations. We anticipate being able to secure several sources of funding for this conference. Approval for Continuing Medical Education credits has been received for this meeting. PUBLIC HEALTH RELEVANCE: This is a request for partial funding support for the fourth annual OSSD meeting (Organization for the Study of Sex Differences), to be held June 3 - 5, 2010 in Ann Arbor, MI. OSSD is a new scientific membership society with a mission to enhance the knowledge of the biological basis of sex/gender differences in human health and disease by facilitating interdisciplinary communication and collaboration among scientists and clinicians from diverse backgrounds.

OSSD is a scientific membership society with a mission to enhance the knowledge of the biological basis of sex/gender differences by facilitating interdisciplinary communication and collaboration among basic scientists and clinical scientists from diverse backgrounds. The main objectives of the Annual Meeting are to: 1) advance the understanding of sex differences throughout the organism; 2) explore the role of biological sex differences across the lifespan; 3) highlight research from top scientists in a variety of biological fields; 4) facilitate the establishment of collaborations among national and international scientists who are interested in the molecular, genetic and hormonal bases of biological sex differences; and 5) grow the scientific community interested and involved in sex differences research by encouraging and supporting the participation of New Investigators who will present talks and posters. Importantly, this grant will support the travel expenses for four New Investigators whose research will be highlighted on the opening day of the conference in the Elizabeth Young New Investigator Symposium. Presenters will gain experience in preparing and delivering a talk at an international meeting. This opportunity should lead to enhanced career opportunities for the New Investigators as well as provide an incentive for other trainees. Additionally, the OSSD is committed to rewarding students and post-doctoral trainees for their intellectual involvement in the field of sex differences. Travel and Poster Awards are given based on the scientific merit of the research, the effectiveness of the presentation, and the role of the trainee in initiating and carrying out the research. The symposia and poster presentations will enhance the knowledge of those studying sex-based biological differences by highlighting new discoveries and by facilitating communication and knowledge-sharing among diverse fields of study.

For many species, including our own, social bonding is essential for numerous aspects of biological and psychological function. Therefore, it is critical to understand the neuroscience underlying social bonding. This project will examine the neurobiology of social bonding by utilizing behavioral, neuroanatomical, and neurochemical assessments of pair bonding in the socially monogamous prairie vole. The experiments will determine how the endogenous opioid systems interact with dopamine signaling in brain circuitry important for reward and motivation underlying pair bond formation and maintenance. Additionally, the project will capitalize on state-of-the-art neurochemical measurement technology (fast-scan cyclic voltammetry) in the prairie vole model to further assess the role of opioid-dopamine interactions in pair bonding. On both intellectual and technical levels, results from these studies are expected to have a tremendous impact on several biological fields. This work focuses on the neuroscience of social bonding, is poised to enhance our understanding of reproduction, ethologically relevant learning and memory, as well as the evolutionary origins of neural mechanisms that mediate social bonding. Importantly, the robust teaching plans will translate into the classroom (at both the graduate and undergraduate levels) and impact how this information will subsequently reach the public domain. Finally, this project provides outstanding training opportunities for both graduate and undergraduate students, revealing details on how students will be trained in the laboratory and placing an emphasis on promoting diversity in neuroscience by the recruitment and training of women and underrepresented minorities into this laboratory.

DESCRIPTION (provided by applicant): Drug abuse among young women is on the rise, with a recent report stating that 56 percent of cocaine users ages 12-17 are women. Women escalate more rapidly through all stages of drug addiction as compared to men, making them especially vulnerable to the deleterious effects of cocaine. Pharmacological treatments for cocaine abuse that are effective in men, such as naltrexone, are ineffective in females or even increase drug use. While it may be possible to develop gender-specific pharmacologic treatments for cocaine abuse in women, non-pharmacologic treatments are also needed. Research in laboratory animals and survey research with humans has indicated a potentially protective effect of the formation of strong social bonds with regards to drug abuse. The strongest social bond formed in rats is the mother-infant bond. Following the rearing of offspring, female rats demonstrate improved learning and memory, increased exploration and foraging ability, attenuated age-related decreases in cognitive function, and decreased neurobehavioral stress and fear responses, even after the offspring have been weaned. These beneficial alterations have been shown to persist for months after the offspring have left the nest, indicating relatively permanent neural reorganization. Importantly, these benefits of maternal behavior occur in nulliparous foster mothers and males that have been induced to act maternally, indicating that pregnancy and parturition are not required for these benefits to be seen. Both drugs of abuse and formation of social bonds induce changes in the neuronal targets of the mesolimbic dopamine pathway, in particular in the nucleus accumbens and striatum. When attachment to a conspecific or drug of abuse is induced, the ability of this neural system to form an attachment to alternate goals is reduced. So, male prairie voles that have pair-bonded with a female do not develop a conditioned place preference to a low dose of amphetamine, while non-bonded males do. Likewise, male voles that have exhibited sensitization to amphetamine do not readily form a pair-bond when presented with a female. Preliminary data from our laboratory have shown that primiparous females exhibit less behavioral sensitization with repeated cocaine administration than do nulliparous age-matched females. The experiments proposed here will test the hypothesis that beneficial effects of social bond formation during the maternal experience of caring for young (whether the female is parturient or not) can protect females from susceptibility for drug abuse. Specifically, experiments will examine if caring for young can affect cocaine self-administration behavior (i.e., the rate of acquisition, the motivation to self-administer cocaine, continuation of responding during periods of non-reinforcement, and persistence to take drug in the face of aversive outcomes), and/or the animals'endogenous response to repeated cocaine exposure using a behavioral sensitization paradigm and in vivo microdialysis. PUBLIC HEALTH RELEVANCE: The experiments proposed here will test the hypothesis that beneficial effects of social bond formation during the maternal experience of caring for young (whether the female is parturient or not) can protect females from susceptibility for drug abuse. Data generated from these experiments will provide a first step towards delineating neurobiological/neurobehavioral mechanisms that may attenuate drug taking in females and lead to identification of new methods to help treat women who are at risk for drug addiction.

DESCRIPTION (provided by applicant): Addiction is a disease primarily characterized by compulsive drug seeking and taking; however, equally devastating is the loss of interest in one's normal activities (e.g., interpersonal relationships, work and recreational activities). Typically, this reduction is viewed as a secondary consequence of the heightened reinforcing value of drugs (i.e., drugs become so important/salient that everything else necessarily pales in comparison). We propose that drugs exert at least two distinct influences on motivation circuits: 1) the enhanced motivation for drugs, mediated primarily by enhanced dopamine (DA) signaling in the nucleus accumbens (NAc), and 2) the loss of interest in natural rewards, which we hypothesize is mediated by enhanced norepinephrine (NE) signaling in the NAc. Individual differences in DA and NE levels are expected to render some more (or less) vulnerable to the development of addiction. NE levels in the striatum are greater in females and vary over the reproductive cycle. Therefore, we propose that one mechanism predisposing women to addiction is their heightened NE levels, which become further exacerbated with drug use. This results in the loss of interest in natural rewards and renders women more susceptible to the reinforcing effects of drugs. Males are less likely to experience these effects to the same degree (due to their relatively lower NE levels); however, with chronic use, drug-induced neuroadaptations in NE signaling may contribute to more severe signs of dependence in both sexes. To test this hypothesis we will examine the effects of adrenergic antagonists in the NAc on the self-administration of cocaine and natural rewards (e.g., food) in male and female rats. We predict that NE antagonists will reduce drug intake by reinvigorating interest in natural rewards, which is suppressed over the course of self-administration, and that this effect will be most pronounced in females. We will also examine sex differences in the NE system, including 21 adrenergic receptors, NE biosynethetic enzymes and innervation in the NAc via immunohistochemistry, and basal and cocaine-induced NE levels in the NAc via microdialysis. The sum of these experiments will lay the groundwork for understanding sex differences in the function of the noradrenergic system in the NAc under basal conditions and following drug exposure and provide a rationale for different pharmacotherapies for men and women in the treatment of addiction.

DESCRIPTION (provided by applicant): Cocaine abuse has increased during the last decade so that 2.4 million Americans currently use cocaine, and of those addicted 39.5 percent are female. Women begin using cocaine and enter treatment at earlier ages than men and have more severe cocaine use at treatment intake than men. In fact, from initial use to dependence female humans and rats progress at a faster rate than males and have greater motivation to obtain cocaine. Current treatments for all substance use disorders (and we lack any medication treatment for cocaine use disorders) do not mitigate stress-potentiated drug use. We have a very limited understanding of sex differences in response to stressors and their effect on drug self-administration, particularly in the context of medication and implications for treatment outcome. While stress augments drug intake and relapse, a positive social environment may serve to reduce drug use. The latter could act by reducing stress levels, and thereby decreasing drug intake. Preliminary data show that pair housing in laboratory rats reduced the motivation to take cocaine in females, but not in males. Oxytocin (OT) is a likely Candidate for bridging the gap between addiction and the protective effects of a social environment. We hypothesize that OT, in combination with social housing, will reduce the motivation to take cocaine. We will investigate whether exogenous OT can reduce the motivation to take cocaine and if this is influenced by the social housing conditions, focusing on females. Furthermore, we hypothesize that OT and pair housing exert their effects by modulating cocaine- induced dopamine release. Therefore, we will investigate if pair- housing and OT, or the combination of both, affect cocaine-induced dopamine release in the nucleus accumbens, comparing cocaine-naive and self-administration-experienced rats. The results from these studies will provide an indication if OT can be used as a therapeutic agent for the treatment of cocaine- addiction, and if the presence of social contacts will augment the effects of OT.

How does the brain decide when it is time to work to obtain food or put its effort into finding a mate? What changes in the brain to assign priorities to specific rewards depending on the internal state of the animal? In these experiments, the investigators will study how the hormone, estradiol, acts in the brain of the female rat to decrease food intake and the motivation for food, while enhancing reproductive motivation. The investigators will study the chemistry of the brain as it responds to the presentation of a cue that has been previously paired with a reward. These studies will investigate how changes in the neurotransmitter, dopamine, is affected by reward-related cues under different hormonal states. These results will enhance the understanding of the role of hormones to influence motivation and decision making processes, and will contribute to the understanding of neuroplasticity in general.

In the female rat, estradiol decreases food intake and the motivation for food while enhancing female reproductive motivation. Further, dopamine (DA) increases in the nucleus accumbens (NAc) upon the presentation of a cue that has been previously paired with a reward, and NAc DA is implicated in attribution of incentive salience for that reward. How DA signaling is affected by reward-related cues under different hormonal states, and the mechanism through which estradiol affects the incentive salience of these cues, is critically important to our understanding of motivation in the female rat. Experiments will use fast scan cyclic voltammetry to measure spontaneous DA release in the core and shell of the NAc during responding for a mate or food under different hormone conditions, using our novel paradigm to quantify female reproductive motivation. The role of DA in mediating the switch from choosing food to choosing a mate in the female will be determined. Graduate students and undergraduates will be involved in these studies. Findings will be disseminated through scientific publications as well as presentations at conferences at the local and national level. Specific activities for students in the laboratory included pre/post assessment of laboratory skills and development of a BrainsRule! presentation to local and Detroit middle school students about the neural mechanisms of motivation and choice.

? DESCRIPTION (provided by applicant): When presented with food or cocaine, dopamine (DA) in the nucleus accumbens (NAc) initially signals that the item is rewarding. When behaviors, such as drug taking, become compulsive we hypothesize that this reflects a shift in neural systems maintaining the behavior. There is enhanced DA release in the dorsolateral striatum (DLS) and attenuation of NAc DA release. Furthermore, within DLS, activity in the Direct Pathway from the striatum to the substantia nigra, that is important for initiation of appetitive behaviors is enhanced, while activity in the Indirect Pathway, from the striatum to the globus pallidus, that inhibits competing repetitive or stereotyped behaviors is attenuated. Females (women and laboratory rats) exhibit more rapid escalation of drug taking than do males and estradiol (E2) enhances acquisition of drug taking and motivation for drugs of abuse. Experiments from the Becker laboratory have demonstrated that E2 inhibits GABA release, down-regulates DA D2 receptors (D2DR), and enhances cocaine- or amphetamine-stimulated DA release in DLS but not NAc. The overarching hypotheses for this proposal are: 1) An attenuated cocaine-induced DA increase in NAc combined with an enhanced DA increase to cocaine in DLS is related to the propensity to develop a preference for cocaine over palatable food pellets in both males and females; 2) Estradiol's action in DLS of females enhances the cocaine-induced dopamine (DA) increase, inhibits GABA release, and inhibits D2 DA receptors. This combined effect enhances the rate of preference formation and motivation for cocaine over pellets in females; and 3) Decreased inhibition of the indirect pathway in DLS contributes to enhanced motivation for cocaine over pellets in both males and females. In females D2DRs are down-regulated in this pathway by E2, and this contributes to the more rapid preference formation in females and greater motivation for cocaine over pellets. Determining the mechanism(s) mediating formation of preference for cocaine over a highly palatable food reward, and how individual differences and sex differences contribute to this, are important for our understanding of and treatment of addiction in both men and women.

Addiction to methamphetamine (METH) is a major public health concern, however there are no effective treatments. Although METH is used by both men and women, women are younger when they start using METH, and show higher rates of dependence compare to men. Women also report a higher exposure to traumatic events and often start using to cope with psychological problems. Social support has a positive influence on stress-coping and might also have protective effects against addiction and help promote decreased motivation to take METH. Females show greater motivation for cocaine than male rats and social housing (pair housing) attenuates the motivation for cocaine in females but not males. Here we investigate whether oxytocin (OT) mediates the effects of social housing on motivation for METH. It is hypothesized that the effects of social housing are mediated by OT-dependent attenuation of dopamine (DA) release in the nucleus accumbens core (NAcC) after drug taking is established and that these effects will be greater in females than in males. Previous research has established that social housing attenuates the METH-induced increase in DA in dialysate from the NAc, and chronic low dose OT attenuates the motivation for METH in female rats. The long- term goal of this project is to understand how social housing influences the rewarding effects of METH in males and females, the role of OT in this regard, and whether chronic intranasal OT may be a therapeutic agent for treatment of psychostimulant abuse in females and/or males. We will also investigate DA responses in the nucleus accumbens fast-scan cyclic voltammetry (FSCV) in isolated and socially-housed male and female rats. The results of these studies will provide an indication of the role of DA in the nucleus accumbens to mediate the effects of social housing and OT on motivation for METH. We will also explore whether chronic intranasal OT can be used as a therapeutic agent for the treatment of METH-addiction.

Project Summary/Abstract Addiction is a major public health concern. Approximately 8.3% of the population needed treatment for addiction in 2013. Cocaine is one commonly used illicit drug that is abused by 10-12% of the population and is highly addictive. During adolescents, equivalent numbers of males and females are abusing or dependent on cocaine. In adults aged 18 and older, the prevalence is double in males compared to females. It is important that we identify why twice as many males are continuing to use after adolescence, and identify novel potential treatment targets that can be beneficial to males. While our lab has historically studied sex differences and especially the characteristics of female drug taking, the studies proposed focus on a novel mechanism that may mitigate drug taking in males. In the proposed work, we investigate a novel mechanism through which the preference and motivation for cocaine is differentially affected in males, but not females. Estradiol (E2) is an important hormone in the brains of both females and males. In males, E2 in the brain is synthesized from testosterone via the enzyme aromatase. In both sexes, E2 acts by binding to one of three types of E2 receptors (ER)s: alpha (?), beta (?), or G-protein receptor -1 (GPER-1). Previous studies have found that E2 potentiates cocaine-induced DA in the dorsal striatum (dSTR) and enhances acquisition of drug taking in females only. The studies proposed will identify how ER activation of GPER-1 differentially influences preference and motivation for cocaine in male and female rats. Our preliminary data show that activation of GPER-1 in the dSTR of male rats blocks conditioned place preference (CPP) for cocaine, but has no effect on CPP in females. Additional preliminary results find that activating GPER-1 attenuates cocaine-induced DA increases within the dSTR of males, but not females. Together, these results suggest that GPER-1 activation may have a protective effect against the rewarding effects of cocaine in male rats, but not females. The experiments proposed will investigate: 1) whether sex differences in GPER-1 receptor activation in the dSTR are related to the preference for cocaine; 2) the effect of GPER-1 on cocaine-induced DA release in male and female rats; and 3) the effect of GPER-1 on the motivation for cocaine in male and female rats during acquisition and after acquisition. Addiction treatment needs targeted treatment for males and females. This work will open new avenues for prevention and treatment of addiction by providing a sex-specific understanding of gonadal hormones the neurobiological mechanisms mediating the rewarding properties of psychostimulants.