Exposure to alcohol alters the activity of the hypothalamic-pituitary-adrenal (HPA) axis. Work carried out in our laboratory as well as other's indicates that prenatal alcohol exposure augments HPA axis activity in mature offspring, while animals chronically exposed to the drug for the first time in adulthood display blunted HPA axis responses. The purpose of this proposal is to investigate some of the mechanisms responsible for these effects. First, we will focus on nitric oxide (NO), a gaseous neurotransmitter that, as we recently reported, significantly stimulates levels of corticotropin releasing factor (CRF) and vasopressin (VP) in the hypothalamus. Specifically, we will test the hypothesis that prenatal alcohol alters (a) hypothalamic levels of NO and NO synthase (NOS), the enzyme responsible for NO formation, (b) the CRF and/or VP neuronal response to NO donors, and (c) the physiological role played by NO, which will be studied with NOS antagonists (Specific Aim 1). Second, we will test the hypothesis that alcohol-induced increases in hypothalamic CRF levels, through activation of a hypothalamic feed forward mechanism previously reported by our laboratory, participates in the hyperactive HPA axis that is the hallmark of prenatal alcohol (Specific Aim 2). At present, there is no information regarding the effect of prenatal alcohol exposure on the HPA axis of murine offspring. As a first step, we will therefore develop a murine model of prenatal alcohol treatment and investigate HPA axis responses in wild-type mice born to dams exposed to alcohol during gestation. These experiments will rely on an automated system that was recently developed in our laboratory, and that allows us to deliver intermittent amounts of alcohol vapors that are customized for each animal. Once the parameters of this new model are established, we will investigate the role of alcohol-induced changes in CRF levels, by exposing to alcohol vapors pregnant wild-type mice and mice lacking the gene for CRF receptors type 1 or 2, and comparing the HPA axis of their offspring. The final part of our proposal will focus on the hypothesis that long-term alcohol vapor treatment of adult rats decreases hypothalamic NO production, thereby contributing to the blunted HPA axis activity that characterizes these animal (Specific Aim 3). All the proposed experiments rely on cutting-edge methodology that was developed in our laboratory, as well as on recent concepts of brain regulation by NO. These studies will provide important information regarding effects of alcohol that are well documented in animal models as well as in humans, but for which mechanisms remain poorly understood.
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