Susan Barron - US grants

DESCRIPTION (provided by applicant): While it is well known that prenatal ethanol (ETOH) exposure has detrimental effects on the developing CNS, there are still numerous questions regarding the mechanisms underlying the CNS damage observed. The effects of ETOH on the glutamate/NMDA receptor (NMDAR) are well established. ETOH-induced alterations in NMDAR function during development causes hippocampal damage by at least two mechanisms; reduced NMDAR function during the presence of ETOH (via apoptosis) and enhanced NMDAR function during ETOH withdrawal (via excitotoxicity). Which of these mechanisms predominates may be age- dependent with suppression of NMDAR activity being more damaging at earlier developmental stages and overexcitation during ETOH WD being a more dominant component in older cultures. Polyamines are ubiquitous compounds that also play an important trophic role during CNS development and one of the mechanisms by which polyamines work is by potentiation of the NMDAR. Since hippocampal NMDAR subtypes and their response to polyamines change during the first neonatal weeks in rats, the timing when ETOH exposure occurs may have significant influences on response to polyamines, NMDAR and outcome. These hypotheses can be tested directly in vitro using the organotypic cell culture model and comparing cultures obtained from neonatal rats at PND 2 versus PND 8. The specific aims are 1) to examine how developmental age affects the response to ETOH as measured by cell damage in our in vitro organotyplc hippocampal model; 2) to examine how developmental age and ETOH exposure interact with polyamines as measured by cell damage in the in vitro hippocampal model and 3) To assess whether in vivo ETOH exposure correlates with the findings from in vitro exposure. The model proposed in this application will provide an innovative and novel approach for using hippocampal organotypic cell cultures to address specific developmental questions related to ETOH's effects and to assess the predictive validity of the model to predict in vivo results. With these findings, it may also be possible to gain a better understanding of some of the mechanisms underlying neonatal ETOH exposure and the role of polyamines that will provide grounds for pharmacological interventions that will reduce some of ETOH effects.

DESCRIPTION (provided by applicant): Fetal Alcohol Spectrum Disorder describes a wide range of behaviors and deficits that can occur as a consequence of prenatal alcohol exposure. These effects can range from relatively subtle learning deficits to significant mental retardation. Various explanations for differences in sensitivity to alcohol's effects have been proposed. One theory suggests that "provocative factors" can play a role in increasing the severity and/or providing a context in which the damaging effects of ethanol are increased. We propose that prenatal alcohol exposure may increase the adverse consequences of brief periods of hypoxia during the antepartum period when brief periods of hypoxia routinely occur. Normally, the fetus/newborn is fairly resilient against mild hypoxia during labor and delivery, however, additional challenges (such as a history of in utero alcohol exposure or alcohol withdrawal) may put these infants at increased risk for adverse outcome. In this application, we propose to develop two models. The first is an in vitro organotypic hippocampal slice culture model taken from 1-day-old rats. These cultures will be exposed to chronic alcohol, followed by withdrawal and challenged with oxygen glucose deprivation (as a model of hypoxia). The hypothesis is that alcohol and hypoxia will produce greater damage than exposure to either challenge alone. Sub-threshold doses will also be included in this Specific Aim to assess the sensitivity of the hippocampus to these challenges. The 2nd model we will develop involves three trimester in vivo administration of alcohol first to pregnant dams and then to Sprague Dawley rat pups on postnatal day 1-7. Following alcohol withdrawal, the pups will also be exposed to a mild hypoxic challenge and subsequently tested for a variety of behavioral endpoints including activity and measures of learning and memory. Our working hypothesis is that alcohol exposure and/or withdrawal and hypoxic challenges share similar mechanisms (including overactivity of NMDAR, increased GLU activity and polyamine release) that could result in increased excitotoxic damage. The studies proposed will allow us to determine the potential validity of these models. In addition, once we have established these models, we can begin to study the underlying mechanisms and potential pharmacotherapeutic interventions to try and reduce the damage/deficits associated with alcohol withdrawal and hypoxia. These data could have significant clinical potential since our premise (and model) focuses on a relatively narrow developmental window which conceptually overlaps a time when women would typically be seeking medical assistance (i.e. labor and delivery) and intervention would be more likely. PUBLIC HEALTH RELEVANCE: Mild bouts of hypoxia (or reduced oxygen availability) commonly occur during normal labor and delivery and the newborn is usually not affected by these if the bouts are not severe. We propose that one of the effects of prenatal alcohol exposure is to increase the risk of these minor bouts resulting in behavioral and CNS damage. The studies in this application will develop cell culture and rodent models to begin to address this clinically-relevant question.