Main Project 1
Prenatal alcohol exposure: Sex differences in effects on adolescent ethanol drinking,
anxiety and associated neural circuitry
PI: J. David Jentsch (email@example.com)
Alcohol consumption by pregnant women remains a startingly common occurrence, despite the well-known potential consequences for the health of exposed children. This is true even when alcohol consumption is moderate, leading some to conclude that there is no safe level of alcohol consumption during pregnancy. One of the most reproducible consequences of even low to moderate levels of prenatal alcohol exposure (PAE) is a heightened ethanol preference and consumption in offspring, a phenomenon found in both human and animal models. Recent evidence from preclinical research has found consistent evidence of a sex-biased effect, with male offspring showing a greater PAE-induced increase in ethanol consumption and preference than females. This effect is observed even when PAE occurs prior to gonadal differentiation (before gestational day 12 in rodents), suggesting that a non-gonadal sex-biasing factor must be responsible. This project tests the hypothesis that genetic differences between males and females (sex chromosome complement and associated differences in expression dosage of X vs. Y chromosome genes) moderate PAE effects. This hypothesis will be tested using Four-Core genotype mice, in which the normal relationship between sex chromosome complement and gonadal sex has been broken; the four core genotypes thus include XX females, XY females, XY males and XX males. We will use this model to systematically test the prediction that XY genotype, irrespective of gonads and gonadally-derived steroids, is associated with heightened PAE-induced escalation of adolescent ethanol intake and heightened anxiety-like behaviors, and that these behavioral effects reflect disturbed inhibitory synaptic signaling via reduced alpha-1-containing GABAA receptor function in the medial central nucleus of the amygdala. Additional studies will test the hypothesis that differential expression of kdm6a – an X chromosome escapee – contributes to the differential responses of XX and XY individuals to PAE. Collectively, these studies will define the mechanisms underlying the sex-biased response to gestational alcohol exposure and may reveal molecular pathways and neural circuits that confer susceptibility to this common environmental insult with pervasive effects on brain and behavior.
Main Project 2
Binge-type alcohol exposure during adolescence alters the septohippocampal circuit
during advanced aging
PI: Lisa Savage (firstname.lastname@example.org)
Converging data from human studies and preclinical animal models have revealed that alcohol binge drinking/exposure during early adolescence is associated with changes in brain structure and connectivity. Persistent brain damage after adolescent intermittent ethanol exposure (AIE) in rodents, a model of binge drinking, entails reduced hippocampal neurogenesis and a loss of cholinergic neurons in the medial septum and diagonal band of Broca (MS/DB). The circuit formed between those regions, the septohippocampal pathway, is critical for learning and memory. The cholinergic projections from the MS/DB to the hippocampus are arranged in a highly topographical pattern, but pilot data suggest a loss of neurogenesis in the hippocampus disrupts the unique somatotopic organization during the aging process. Furthermore, we observed that as rats aged following AIE, a spatial memory impairment emerged, which was paralleled by a reduction in activity-related acetylcholine release within the hippocampus. The goal of this proposal is to reveal how heavy intermittent alcohol exposure during adolescence alters brain connectivity, neural plasticity and behavioral function across the lifespan. Specifically, we will determine how aging following AIE (a) alters the topographical organization of the cholinergic septohippocampal pathway and impedes the expression of cholinergic neural phenotypes within the MS/DB, which modulate activity-dependent hippocampal acetylcholine release (Aim 1); (b) disrupts the neurophysiological profile of cholinergic septohippocampal pathway and leads to behavioral and acetylcholine dysfunction across septotemporal axis of the hippocampus (Aim 2). Finally, given that the septohippocampal circuit is extremely pliable to environmental conditions, we will use exercise as a tool to restore hippocampal neurogenesis, prevent MS/DB cholinergic atrophy/cell loss, and halt dysfunctional remapping to the hippocampus, caused by aging with AIE, which we hypothesized leads to impaired spatial behavior and blunted activity-dependent acetylcholine release (Aim 3). Our preliminary data revealed a profile of septohippocampal dysfunction that resembled alcohol-related dementia as rats exposed to AIE begin to age, and the goal of this proposal is to understand this complex process so it can be corrected to reduce the risk of cognitive dysfunction and unsuccessful aging.
Main Project 3
Developmental sensitivities to alcohol: Opposing actions of cytokines on fear conditioning
during intoxication and withdrawal
PI: Terrence Deak (email@example.com)
Alcohol use and abuse represents a substantial threat to public health. Age of first alcohol exposure is a critical determinant of developmental trajectory and subsequent health status later in life, with prenatal and adolescent periods emerging as developmental epochs during which alcohol exposure is particularly prevalent. Neuroimmune consequences of alcohol have emerged as novel mechanisms that may contribute to changes in alcohol reinforcement, dependence, and ultimately the development of alcohol-related brain damage. Importantly, exposure to acute, binge-like doses of ethanol (EtOH) in rodents produce time-dependent changes in cytokine expression in which Interleukin-6 (IL-6) is substantially elevated in key limbic structures (amygdala, PVN and hippocampus) during acute EtOH intoxication. In contrast, expression of both IL-1β and TNFα tends to surge in these same structures during withdrawal from acute EtOH intoxication. These findings suggest that adolescent rats may have a functionally immature neuroimmune response relative to young adults. Paradoxically, however, adolescent Chronic Intermittent EtOH (CIE) exposure sensitize3d the intoxication-related IL-6 response evoked by a binge-like dose of EtOH later in life (P70 young adults). Thus, adolescents appear to be less sensitive to acute EtOH-induced cytokine responses, while at the same time being vulnerable to long-term sensitization of neuroimmune processes resulting from adolescent CIE exposure. However, the functional significance of these acute, EtOH-induced cytokine changes observed across the intoxication-withdrawal cycle remain obscure. This proposal will utilize contextual fear conditioning procedures as an animal model of emotional learning, and to test the functional relevance of EtOH-dependent expression of cytokines. Consistent findings demonstrate that EtOH impairs fear conditioning when training occurs within a short time-frame after EtOH exposure (i.e. during intoxication), whereas conditioning during EtOH withdrawal tends to enhance fear conditioning. Our central hypothesis is that phase-specific expression of cytokines in the basolateral amygdala (BLA) produce opposing actions on BLA excitability and subsequent fear conditioning. These studies will also examine long-term adaptations in neuroimmune function and resultant consequences following adolescent CIE. In this way, the proposed studies will be among the first to examine how phase-specific, EtOH-induced cytokine expression translates into age-specific, cognitive and behavioral outcomes of early EtOH exposure.
Main Project 4
Sex-specific neural contributors to high social drinking in adolescence
PI: Linda Spear (firstname.lastname@example.org)
Alcohol is one of the most widely used substances by American adolescents, with binge and heavy drinking evident in almost two thirds of underage current drinkers. These high rates of binge and heavy drinking are alarming, since adolescents who engage in even episodic heavy drinking are more likely to exhibit alcohol use disorders and other adverse consequences later in life. Young people predominantly drink in social situations, although this context specificity – let alone sex differences in sensitivity to social consequences – has been little investigated. Using a rat model of adolescence, we have shown pronounced qualitative sex differences in the precursors and effects of ethanol contributing to high social drinking among adolescents. High social drinking among males is associated with high social activity and enhanced sensitivity to the socially anxiolytic effects of ethanol, whereas in adolescent females, higher levels of social drinking are associated with elevated social anxiety and enhanced sensitivity to the socially anxiolytic effects of ethanol. The present proposal is designed to separately determine brain regions that are responsible for high social activity and sensitivity to ethanol-induced social facilitation in adolescent males, in contrast to regions related to high social anxiety and enhanced sensitivity to the socially anxiolytic effects of ethanol in females. Target brain regions that are differentially activated in males and females with high school drinking phenotypes will be determined using transgenic cFos-LacZ rats and X-Gal staining for c-Fos. The Daun02 procedure will then be used to selectively inactivate neuronal ensembles in specified target regions that were activated by the social stimulus alone in combination with acute EtOH, and consequences of this inactivation on subsequent social drinking determined in male and female high social drinkers. We expect that inactivation of neural ensembles activated by social interactions alone or in combination with acute EtOH in high socially active males will attenuate social drinking in these animals, whereas inactivation of neuronal ensembles activated in high socially anxious adolescent females by social stimuli will diminish social drinking in these females. Given the critical importance of brain vasopressin/oxytocin peptide systems in regulation of social behavior and social anxiety, we will also test the hypothesis that high social drinking in males is associated with hyperactivity of the brain vasopressin V1a receptor, whereas functional hypoactivity of the brain oxytocin system contributes to high social drinking in adolescent females. These hypotheses will be tested neuropharmacologically and via assessment of protein levels for oxytocin and vasopressin and their receptors in the brain regions sex-specifically associated with high drinking phenotypes. The work outlined in this proposal will be among the first to examine neural contributors to the pronounced qualitative sex differences in precursors leading to high social drinking among adolescents, and are essential for creation of new, sex-specific early prevention and intervention strategies for heavy alcohol use in adolescence.