The profound and deleterious effects that ethanol exerts on the developing brain are well established, yet the mechanism(s) involved in its neurotoxic effects remain elusive. Receptors for neurotransmitters and growth factors and their cell signaling systems are increasingly recognized as playing relevant roles in various aspects o rain development. In the last few years we have pursued the hypothesis that the metabolism of phosphoinositides coupled to activation of acetylcholine muscarinic receptors may represent a relevant target for the developmental neurotoxicity of ethanol. Our studies have shown that ethanol exerts a dose-, age-, brain region- and neurotransmitter - specific inhibition of this biochemical response, and have demonstrated a strong correlation between disruption of muscarinic receptor - stimulated phosphoinositide metabolism during the brain growth spurt and long-lasting microencephaly. As proliferation of glial cells is a major event occurring during the in growth spurt, and following observations that acetylcholine can act as a mitogen in astrocytes, we have formulated the hypothesis that disruption of acetylcholine - driven glial cell proliferation may play a primary role in the developmental neurotoxicity of ethanol, and may provide a direct causal link between the observe inhibition of phosphoinositide metabolism and the ensuing microencephaly. The focus of the propose -experiments has shifted from investigations of the effects of ethanol in vivo or in vitro in brain slices or mixed cultures, to the study of its interactions with a selected glial cell population (astrocytes) in vitro. We believe that this shirt represents a logical progression toward a more comprehensive understanding of the sequence of event :hat may link our initial observations of the effects of ethanol on phosphoinositide metabolism to the observe neurotoxic endpoints, such as microencephaly.
The specific aims of this proposal are: 1. To investigate selected signal transduction pathways involved in the mitogenic effect of acetylcholine in cultured cortical astrocytes. These will include the hydrolysis of phosphoinositides and phosphatidylcholine, mobilization of intracellular calcium, activation of protein kinase C and induction of immediate - early - genes. 2. To investigate the molecular pathways involved in the observed inhibition by ethanol of the mitogenic action of acetylcholine in astrocytes.
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