SPECIFIC AIMS This proposal continues our investigation of ethanol effects on the mammalian circadian clock located in the suprachiasmatic nucleus (SCN). Alcohol use, abuse and withdrawal have profound effects on sleep and circadian rhythms. Alcohol effects on these two processes likely are closely intertwined since disruptions in circadian functioning are major causes of many sleep irregularities. The long-term goal of our research is to better understand the neural processes contributing to the etiology of these sleep problems, specifically focusing on the role circadian rhythmsOur collaborative research shows that ethanol inhibits photic phase resetting of the SCN circadian clock in vivo and in vitro. The objective of this RO1 proposal is to identify the cellular mechanisms underlying the acute effects of ethanol, and to expand our research to investigate the effects of chronic alcohol and alcohol withdrawal. The major advantage of our collaboration is our ability to interweave complementary in vivo and in vitro experiments that take advantage of the unique aspects of each approach. Our central hypothesis is that ethanol inhibits glutamate signaling in core SCN neurons, which over time leads to up-regulated glutamatergic activity. Our rationale for the proposed studies is that identifying the cellular mechanisms through which ethanol modulates the circadian clock will lead to new insights on treatments that may prevent or overcome this debilitating disease. Therefore, we proposed to pursue the following specific aims: Specific Aim 1. Determine time-dependent changes in ethanol effects on photic/ glutamate signaling in the SCN: acute vs. tolerance vs. chronic vs. withdrawal. These experiments will characterize the effects of ethanol on the SCN circadian clock through monitoring behavioral and electrophysiological (in vivo and in vitro) rhythms, and how these effects vary depending on the duration of ethanol exposure. Specific Aim 2. Determine the cellular mechanisms of ethanol actions in the SCN. These experiments will assess the effects of ethanol on in vivo SCN neuropeptide release patterns, and investigate the cellular mechanisms through which ethanol inhibits glutamate-induced phase resetting in vitro. Specific Aim 3. Determine how ethanol affects non-photic phase resetting. These experiments will assess the effects of acute and chronic ethanol, and ethanol withdrawal, on serotonergic, GABAergic, and NPYergic phase resetting in vivo and in vitro, and probe the mechanisms and locations through which these effects occur.