Elliott Albers, Ph.D. - US grants

This is the continuation of a project to investigate how mammalian circadian rhythms are generated, and synchronized with the 24 hr light-dark (LD) cycle. The role played by the putative neurochemical messengers found within the suprachiasmatic nucleus (SCN) (i.e., vasopressin, somatostatin, vasoactive intestinal peptide and gamma aminobutyric acid) in the generation of circadian rhythms will be investigated by determining how the microinjection of these substances (and antagonists and antisera) influence the circadian control of hamster wheelrunning activity. Whether a second circadian clock exists within the hamster circadian system will be determined by destroying the SCN and examining whether the circadian rhythm of core body temperature persists, and whether it can be synchronized by the LD cycle. The functional, neurochemical and anatomical bases of the synchronization of circadian rhythms to the LD cycle will be investigated in both a nocturnal (hamster) and diurnal (ground squirrel) mammal by: 1) defining the importance of each specific component of the LD cycle (i.e., light, the transition between light and dark; darkness, the transition between dark and light) in the synchronization of circadian rhythms by determining how each of these LD cycle components phase shift circadian rhythms, 2) defining whether the putative neurochemical messengers that appear to be contained in the two major visual afferents of the SCN (i.e., LANT-6 in the retinohypothalamic tract and neuropeptide Y in the lateral geniculate - SCN projection) can mimic the phase shifts produced by specific components of the LD cycle when microinjected into the SCN region, and 3) determine whether different visual projections to the SCN communicte different types of visual information about the LD cycle to the SCN by determining how the different components of the LD cycle phase shift circadian rhythms following lesions that destroy the lateral geniculate nucleus. By understanding how circadian rhythms are generated and synchronized with the environment, it will be possible to provide effective treatments for the increasing number of health problems linked to disorders of the circadian timing system.

Hormones secreted from the gonads have a major impact on the behavior of mammals. Most of the behavioral effects of gonadal hormones are thought to be mediated by the central nervous system; however, very little is known about the underlying mechanisms. This project will use a functionally significant communicative behavior of the hamster as a model system to study how gonadal hormones interact with the brain to control behavior. The communicative behavior to be studied, called scent marking, was chosen as a model because one of the neurochemicals (i.e. vasopressin) essential in the central nervous system control of this behavior has been identified and appears to function within a specific site of the brain (i.e. the medial preoptic-anterior hypothalamus). After the effects of gonadal hormones on scent marking behavior have been fully established, this project will investigate whether gonadal hormones influence scent marking by acting on cells which produce or respond to vasopressin within the medial preoptic-anterior hypothalamus. These studies should provide new information on how the nervous and endocrine systems interact to control behavior.

Steroid and peptide hormones have a major impact on the behavior of mammals. While it is believed that many of the behavioral effects of hormones result from their action on the central nervous system, how hormones change brain function to influence behavior is not well understand. Dr. Albers, who has previously received support from the National Science Foundation, will continue his work on steroid-peptide-transmitter interactions, a general problem of substantial interest in neurobiology. Sophisticated anatomical and biochemical techniques are used to examine a sexually dimorphic communicative behavior which has proven to be an excellent model system. Specifically, Dr. Albers will focus on three different brain sites where it is believed that vasopressin, a neuropeptide, interacts with the gonadal steroid hormones testosterone and estradiol to regulate communicative behavior. He will determine whether the gonadal steroids influence the behavior by changing the amount of vasopressin that can be released at these brain sites or by changing its sensitivity at a particular brain site. Moreover, Dr. Albers will explore the interconnections of the three brain regions implicated in the control of this behavior and thus, provide new information about their neural circuitry. He will also investigate whether social factors that influence the expression of this communicative behavior do so by altering the activity of vasopressin in the brain. Finally, a carefully designed set of pharmacological studies will be carried out to determine how the noradrenergic transmitter system is involved in coordinating the expression of this communicative and other behaviors. The results from these studies will make an important contribution to our understanding of the basic mechanisms underlying the relationship between the nervous and endocrine systems in the regulation of behavior.

This project will investigate how several neurotransmitter systems interact to control circadian rhythms in behavior. Understanding the basic principles underlying the neurobiology of circadian rhythms should lead to the development of new treatments for a variety of mental illnesses. The unifying theme of this proposal is that GABAergic neurons within the suprachiasmatic nucleus of the hypothalamus (SCN) play a critical role in regulating the phase shifting of circadian rhythms. We will test the general hypothesis that GABA alters the phase shifting capacity of the three major afferents to the SCN (i,e. the retinohypothalamic tract, the geniculohypothalamic tract ant eh projection from the raphe) as well as the phase shifting capacity a group of neurons intrinsic to the SCN. Specifically, we will investigate how GABA interacts with the primary neurotransmitters in the afferent projections (i.e. glutamate, neuropeptide Y (NPY) and serotonin) as well as with the major neurotransmitters within the ventrolateral SCN (i.e. vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI) and gastrin releasing peptide (GRP)). Specific aim 1 will test the hypothesis that GABAergic activity within the SCN mediates the phase shifting effects of both NPY and serotonin during the middle of the subjective day (i.e. circadian time 6). Specific aim 2 will test the hypothesis that GABAergic drugs block the phase delaying effects of light at the beginning of the subjective night (i.e. circadian time 12-14) by their effects on glutamate or serotonin activity within the SCN. Specific aim 3 will test the hypothesis that GABAergic drugs modulate the phase delaying effects of VIP, PHI and GRP that occur at circadian time 12-14.

DESCRIPTION (Adapted from applicant's abstract): This project will investigate how neurochemical signals interact within the SCN to synchronize circadian rhythms in behavior with the day-night cycle. Since disorders of the circadian timing system have been linked to a variety of mental illnesses, understanding the neurobiology of circadian rhythms should lead to the development of new treatments for these diseases. At least three different afferent projections of the SCN are involved in the photic entrainment of circadian rhythms. The RHT is a direct projection from the retina that is necessary and sufficient for entrainment. Projections from the raphe and the intergeniculate leaflet to the SCN also influence entrainment although they do not provide input necessary for the entrainment process. The neurochemical signals contained in these afferent projections as well as in neurons intrinsic to the SCN interact in a complex manner to control photic entrainment. The long-term goal of this project is to define the neurochemical basis of the entrainment of circadian rhythms by defining how photic information is communicated to and processed within the SCN. Specific Aim I will test the hypothesis that an EAA is a neurotransmitter which communicates photic information to the SCN through the RHT. Since the investigator has been able to demonstrate that injection of an EAA agonist (i.e., NMDA) into the SCN in vivo can mimic the phase shifting effects of light, it will be possible to resolve a significant discrepancy about this hypothesis. Specific Aim 2 will test the hypothesis that substance P, which appears to be contained in the RHT, contributes to the entrainment by modulating the activity of EAAs in the SCN. Specific Aim 3 will investigate how the phase shifting effects of light are influenced by intrinsic SCN circuits and by afferent projections of the SCN. Specifically, the investigator will test the hypothesis that GABA, serotonin and NPY inhibit the phase shifting effects of light by inhibiting the phase shifting effects of EAAs and/or substance P in the SCN.

How brain mechanisms regulate and are regulated by complex social behaviors across animal species is one of the greatest challenges for neuroscience. This Science and Technology Center for Behavioral Neuroscience brings together a diverse group of behavioral biologists, psychologists, neuroscientists, molecular biologists and engineers from a mix of research-intensive and teaching-oriented institutions in the Atlanta area, including five Historically Black Colleges and Universities. A novel intensive collaboratory approach introduces modern molecular biology into behavioral research with an explicitly comparative aspect. A novel perspective is taken on how brain function, even at the molecular level, may be influenced by particular kinds of social behavior among individuals. Comparing different species offers insights about the conservation of genes and circuits during evolution, and it may transform the way we think about how hormones influence behavior, how genes are regulated, and how brain mechanisms have been adapted for different environmental demands. Six core facilities are formed for technical developments to allow answering scientific questions that previously could not be asked. The research of this center will produce new discoveries, and the integration of research and education for a broad diversity of students will promote a new generation of interdisciplinary neuroscientists.
The impact of this Center extends beyond the scientific advances. The infrastructure of this Center creates a new network of research and educational institutions in the Atlanta area to provide a strong local focus, where excellent facilities and researchers from diverse backgrounds also offer outstanding opportunities for underrepresented groups at all educational levels. Taken together, these features make this Center an exceptional investment by NSF for research and education with a high quality and a high impact.

This project will investigate the neural and endocrine mechanisms that control social behavior in Syrian hamsters (Mesocricetus auratus). There is a substantial body of evidence that the actions of arginine-vasopressin (AVP) within a zone that extends from the medial preoptic area to the anterior hypothalamus (referred to as the MPOA-AH) plays a critical role in the expression of a form of scent marking called flank marking as well as aggression. Understanding the neurobiological mechanisms controlling social behaviors like flank marking and aggression requires definition of the neural/hormonal mechanisms that control these behaviors as well as how experience changes these mechanisms so that these behaviors are continuously adjusted to the changing environment. The proposed experiments will test the working hypothesis that experience alters the expression of flank marking and aggression by its effects on AVP receptors within the MPOA-AH. This hypothesis will be tested by examining the effects of two types of experience that have significant, yet very different effects on scent marking and aggression. First, we will determine whether social experience (i.e. prior agonistic encounters) alters these receptors and will test the prediction that a testosterone-dependent as well as a testosterone-independent mechanism mediates these effects. Second, we will determine whether environmental experience (i.e. exposure to winter-like short photoperiods) alters these receptors and will test the prediction that a testosterone-independent mechanism mediates these effects. We believe that analysis of the effects of such different types of experience on these AVP receptors will provide a rigorous initial test of our hypothesis that these receptors represent a critical regulatory site in the control of scent marking and aggression. These data should provide new insights into the basic principles that govern how neural and endocrine mechanisms control complex social behaviors. This information is critically important for understanding the etiology of a variety of behavioral and emotional disorders as well as the development of new treatments for these disorders.

The goal of this project is to develop approaches to manipulate gene function in non-traditional animal models to understand the role of the vasopressin receptor gene in regulating social behavior. Silencing or disrupting genes in mice has also helped to understand how certain genes influence behaviors. However, mice are not ideal for studying many aspects of behaviors, including social behaviors. Comparative biology uses a wide variety of species with particular characteristics that make them ideal for studying the particular questions. For example, prairie voles are a monogamous rodent species that have been used to understand how molecules act within certain brain circuits to promote social bonding. Hamsters are more solitary and display robust territorial behavior, and have been used to investigate the roles of brain molecules in social communication. However, the utility of these non-traditional species for understanding the roles of specific genes in controlling behavior has been limited because of the inability to manipulate genes. The goal of this project is to use parallel approaches in hamsters and prairie voles to silence the vasopressin receptor gene using two different approaches. One approach will effectively silence vasopressin receptor gene expression, while the other will introduce a mutation in the gene, making it ineffective. By manipulating the expression of this gene, more insights into its role in regulating social behaviors, including social bonding and territorial behaviors will be achieved. Furthermore, the development of these approaches should be applicable to a wide range of mammalian species that are useful for studying different questions. The development of these approaches in hamsters and prairie voles will be transformative for comparative behavioral neuroscience. This project will engage students, ranging from high school to graduate school, in comparative studies addressing the underlying neurogenetics of social behavior. Also, partnerships with Zoo Atlanta will be instrumental in developing new research and educational exhibits that will serve to educate the public on the neurogenetics of social behavior.

DESCRIPTION (provided by applicant): The most important function of circadian clocks is the synchronization of bodily activities with the 24 hr light-dark (LD) cycle through a process called entrainment. The critical importance of entrainment to human health has been demonstrated in both human and animal studies. Desynchrony of the entrainment process produced in the real world by shift work or experimentally by chronic phase shifts of the LD cycle increases the incidence of many disease states including cancer, cardiovascular disease and metabolic disorders. Understanding how the etiology of the disorders produced by disruptions in entrainment will require understanding the neural mechanisms controlling entrainment in the master circadian clock located in the suprachiasmatic nucleus (SCN). The overall goal of the proposed research is to identify the neural mechanisms responsible for entrainment of circadian rhythms in the SCN. Remarkable progress has been made in understanding how the dorsomedial SCN functions as a molecular circadian clock as well as how the ventrolateral SCN responds to light however the neural mechanisms responsible for linking these two critical functions remains unclear. Perhaps this is because light has long been considered to reset the circadian clock instantaneously (i.e., non-parametric entrainment), resulting in the general assumption that the neural mechanisms within the SCN responsible for communicating light to the clock in the core would be of a very short duration. In contrast, we propose that the neural mechanisms that link these two important circadian functions operate over several hours and that GABA is the critical neurochemical messenger. These studies will test the hypotheses that the sustained activation of GABA receptors within the SCN mediates the phase shifting effects of light, the induction of clock genes within the SCN, and that the effects of GABA are mediated by GABA-A-TONIC and not by GABA-A-PHASIC or GABA-B receptors. If we confirm that the sustained activation of GABA receptors over several hours mediates the effects of light in the SCN, it seems likely that this same type of sustained activation of GABA receptors might mediate specific functions in other CNS sites as well. In addition, these studies will provide important new information on functions of GABA receptor subtypes and their possible interactions that should be relevant to GABA action throughout the CNS. Understanding how GABA acts in the brain is extremely important clinically because of the many drugs that target GABA receptors for diseases ranging from epilepsy to anxiety. PUBLIC HEALTH RELEVANCE: Human and animal research have found that desynchrony of the temporal organization of the body produces a wide range of health problems including increased incidence of cancer, cardiovascular disease and sleep-wake disorders that affect millions of people. Since these desynchronies often result from disruptions in the process of circadian entrainment it is critical to understand the mechanisms that underlie entrainment in the master circadian clock located in the suprachiasmatic nucleus. This project aims to identify these mechanisms and thereby provide an understanding of how circadian desynchrony can produce these pathologies.

Project Summary Neuropsychiatric illnesses represent a wide range of complex emotional and behavioral disorders, but many of these are associated with maladaptive social responses. Unfortunately, we do not have a clear enough understanding of the neural mechanisms underlying these disorders or the fundamental symptoms they share. While it has become clear that there is a substantial overlap in the neural circuitry (i.e., the Social Behavior Neural Network) controlling different social and emotional behaviors, the technology to study how behavior emerges from such a complex interacting neural network has been lacking. Variation in social behavior, both across species and within individuals of given species, arises at least in part from genetic and epigenetic differences within the Social Behavior Neural Network, and we are now in a position to understand the molecular mechanisms mediating this variation. These genetic differences are expressed as variations in critical molecular elements of neural circuits such as neurotransmitters, receptors, transporters, growth factors, etc. A significant current limitation to progress in this area is that there are no well-established genome- engineering technologies for some of the best animal species for studying social behavior and organization. Among these organisms are Syrian hamsters (Mesocricetus auratus), which have proven to be an exceptionally useful rodent model for the study of social behavior and for which there is a wealth of data, much of which has been generated by the PIs, on the neurobiological and hormonal mechanisms controlling social recognition, social avoidance, aggression, and social communication. The goal of this project is to overcome this limitation by developing and implementing state of the art genome engineering technologies in the Syrian hamster model to enable molecular interrogation of how genes act within neural circuits to regulate complex social behavior. To achieve this goal, we will use genome engineering to generate transgenic and gene- targeted mutant hamsters that will be used to investigate the function of genes that have been implicated in social behavior. The generation of these transgenic and gene-targeted hamsters will be facilitated by our recently generated Syrian hamster transcriptome data, which will be used to specifically target and manipulate a variety of neurobehaviorally-relevant hamster genes. Initially, as a proof of principle, we will focus on the arginine-vasopressin V1a receptor because of the significance of this receptor in regulating a wide range of distinct social behaviors and our long-demonstrated expertise with studying this system. The successful development of transgenic and gene-targeting approaches for Syrian hamsters will provide transformative tools to the research community for exploring the neurogenetic bases of social behaviors.

PROJECT SUMMARY In most mammalian species, social interactions among individuals of the same species are governed by dominance relationships. These hierarchical relationships are established and maintained by agonistic behaviors, including aggression. Importantly, recent data indicate that the neural mechanisms underlying aggression and attaining dominance produce a phenotype that is resistant to social stress while the mechanisms underlying subordinate status produce a social stress-susceptible phenotype that may result in a number of adverse behavioral and physiological outcomes. Despite the relationship between social status and stress, the neurochemical mechanisms that underlie dominance have received only limited attention in males and almost no attention in females. This project will fill this critical gap in our knowledge by testing an integrated series of hypotheses using Syrian hamsters and rhesus monkeys. This project will critically test the overarching hypothesis that the agonistic behaviors responsible for the formation and maintenance of dominance relationships are regulated in dramatically different ways by vasopressin (AVP) and serotonin (5- HT) in males and females. Specifically, we propose that activation of AVP and inhibition of 5-HT promotes dominant status and a stress resistant phenotype in MALES while producing subordinate status and a stress susceptible phenotype in FEMALES. In contrast, inhibition of AVP and activation of 5-HT promotes dominance and a stress resistant phenotype in FEMALES while producing subordinate status and a stress susceptible phenotype in MALES. Together, these data will significantly expand our knowledge of sex differences in the neurochemical mechanisms that define social phenotypes and will provide innovative gender specific strategies for promoting resistance to social stress. The data obtained in this project could have an almost immediate clinical impact by guiding drug treatments for stress reduction in men and women as well as guiding drug development by emphasizing the role of AVP-targeted drugs in males and 5-HT- targeted drugs in females.

PROJECT SUMMARY The rewarding properties of social interactions are critical to the expression of adaptive social behavior and to the development and maintenance of social relationships. Little is known, however, about the factors that determine the reward value of social interactions or about the basic neural mechanisms that underlie social reward, particularly in females. We do know that the mesolimbic dopamine system (MDS) is central to the neural circuitry controlling the rewarding properties of many other stimuli such as drugs of abuse. A primary component of the MDS is dopamine (DA)-containing neurons in the ventral tegmental area (VTA) that project to the nucleus accumbens (NAc) as well as to other sites such as the medial prefrontal cortex. Critical inputs to the MDS include oxytocin (OT)-containing projections from the hypothalamus. We and others have demonstrated that, in male rodents, activation of OT receptors in the caudal VTA and in the NAc is essential for the rewarding properties of social interaction. Remarkably, despite the considerable evidence for sex differences in OT regulation of social behaviors, the role of OT in regulating social reward in females has not been investigated. This project will provide substantial new information on the factors that determine the reward value of social interactions and on the neural mechanisms that mediate social reward by testing this series of integrated hypotheses in male and female Syrian hamsters. Based on published and preliminary data from our lab and others, we have hypothesized that: 1) there is an inverted U relationship between the ?dose? of social interactions and social reward, 2) this dose-response relationship is initiated at lower doses in females than in males, and 3) this sex difference is mediated by differential OT-induced DA release in the MDS. This project has substantial potential for translation to clinically-related problems by providing: 1) new information on how social stimuli can transition from being rewarding to being less rewarding or even aversive, 2) potential mechanisms for understanding well-known sex differences in the incidence of neuropsychiatric and neurodevelopmental disorders for which dysfunctional social relationships are an important symptom, and 3) the potential for development of gender- specific treatments for these disorders.