AC1 and AC8 as Mediators of the Dendritic Response to Ethanol in a Model of FASD

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Project Summary/Abstract The overall objective of this proposal is to define the mechanisms underlying the deleterious effects caused by ethanol on neuronal morphology in a model of Fetal Alcohol Spectrum Disorder (FASD), thereby upholding the mission of the NIAAA to increase the understanding of biological functions relating to alcohol use. The synaptogenesis (brain growth spurt) period occurs during the last trimester of human gestation and is a critical window for dendritic growth and spine development in the developing brain. Dendritic spines are the primary structures used in synaptic communication between neurons. Exposure to ethanol during this period has been shown to have detrimental effects on the developing fetal brain, leading to learning disorders, behavioral abnormalities, and mental retardation, termed FASD. BDNF has been shown to regulate dendritic growth and spine development through its interaction with the trkB receptor. BDNF expression has also been shown to be modulated by ethanol in various regions of the neonatal brain. Fetal genotype has been shown to affect the severity of FASD as shown by twin studies, although the gene(s) involved have yet to be identified. Since studies have shown adult mice lacking the adenylyl cyclases 1 and 8 have an increased susceptibility to the sedative effects of ethanol, and the striatum of neonatal mice lacking these ACs are more sensitive to EtOH induced neuronal cell death than WT mice, we believe the ACs could play a role in the sequelae of neonatal EtOH exposure. This proposal will test the hypothesis that the Ca[2+]-stimulated adenylyl cyclases (AC1 and AC8) regulate the dendritic response to ethanol through regulation of BDNF signaling. This hypothesis will be tested using the following Aims: 1) Determine the effects of ethanol exposure on neuronal morphology in the developing striatum from wild type (WT) and Ca[2+]-stimulated AC knockout (DKO) mice; 2) Dissociate the pre- and postsynaptic roles of the Ca[2+]-stimulated ACs in the regulation of dendritic complexity and spine formation; 3) Determine the effects of the Ca[2+]-stimulated ACs on BDNF regulation in the neonatal striatum following ethanol exposure. In Aim 1, P5-7 pups (WT and DKO) will be treated with ethanol and striatal neurons will be analyzed at P14 and P30 for soma size, dendritic length, dendritic branching, and spine density. In Aim 2, corticostriatal co-cultures from WT and DKO mice will be used to determine the pre- and postsynaptic roles of the Ca[2+]-stimulated ACs in ethanol-induced effects on dendritic arborization and spine formation. In Aim 3, BDNF mRNA and protein as well as trkB protein will be measured in synaptosomal fractions from ethanol-treated neonatal mice (P5-7) and confocal imaging of striatal neurons will be used to identify the pre- and postsynaptic roles of the Ca[2+]-stimulated ACs in regulating BDNF expression. Training in the use of four main areas: primary neuronal culture techniques (corticostriatal co-cultures), immunohistochemical techniques/confocal analyses, use of diolistic fluorescent dye imaging and neuronal morphology analyses represents exciting opportunities of research for both the sponsor and applicant, greatly enhancing the applicant¿s potential for future scientific success.