The role of GLT1 in the modulation of alcohol-drinking behavior in P rats.

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DESCRIPTION (provided by applicant): Alcohol (EtOH) abuse and dependence continue to be significant public health problems. Thus, a better understanding of their neurobiology will facilitate the development of interventions targeting prevention and/or treatment of these major health issues. Emerging evidence indicates that many aspects of EtOH and drug dependence involve changes in glutamate transmission. Because glutamate transporter 1 (GLT1) is responsible for the uptake of the majority of extracellular glutamate, we tested the hypothesis that increased GLT1 function would attenuate EtOH consumption in alcohol-preferring rats (P rats). After P rats had been chronically exposed to a free choice of EtOH (15 and 30%) for five weeks, they were administered ceftriaxone (i.p.), a beta-lactam antibiotic known to elevate GLT1 expression, for five consecutive days. We found that ceftriaxone-treated P rats showed a reduction in EtOH intake for the duration of treatment as compared to rats that received a saline vehicle. The long-term effects of ceftriaxone, however, are unknown. Here, we will test the long-term effects of ceftriaxone and other drugs (GPI-1046 and MS-153) known to activate GLT1 in the attenuation of EtOH intake at two different time points of chronic EtOH exposure in P rats. We will also investigate the effects of GLT1 activation in EtOH-drinking behavior in Wistar rats as comparison control groups. Our working hypothesis in aim 1 is that an increase in GLT1 function, via up- regulation or activation, attenuates EtOH consumption in both P and Wistar rats. The EtOH deprivation effect, which we will employ, has been used to assess relapse-like behavior in P rats. In aim 2, our working hypothesis is that an increase in GLT1 function during withdrawal periods will reduce relapse-like behavior when animals are re-exposed to EtOH. The lowest tested dose of ceftriaxone (25 mg/kg), which did not show an increase in GLT1 expression, was also effective in reducing EtOH intake. These findings suggest that ceftriaxone may have other pharmacological effects on GLT1 or may act by another mechanism (a functional increase may involve a change in one of several mechanisms). Thus, we propose in aim 3 to determine the signaling pathways involving ceftriaxone or GPI-1046 in up-regulation of GLT1 expression. Moreover, we aim to determine the molecular mechanisms of action of ceftriaxone, GPI-1046 and MS-153, which may involve activation of GLT1 function through phosphorylation of key proteins. The findings generated from this proposal will provide ample information about the role of GLT1 in the regulation of EtOH consumption and will pave the path toward finding a potential therapeutic target for alcohol addiction.