Youssef Sari

Adjunct Assistant Professor of Medicinal and Biological Chemistry University of Toledo, College of Pharmacy & Pharmaceutical Sciences Department of Pharmacology Health Science Campus, Mail Stop 1015 3000 Arlington Avenue, HEB283C Toledo, OH 43614, USA

Abstract:

We have previously reported that administration of ceftriaxone, a ..-lactam antibiotic known to elevate levels of one of the glial transporters such as glutamate transporter 1 (GLT1), has a longlasting effect in reduction of ethanol intake in alcohol-preferring (P) rats. Since it has been shown that deletion of equilibrative nucleoside transporter 1 (ENT1) was associated with reduced GLT1 expression or function, we first determined in this study for changes in the levels of GLT1 and ENT1 in prefrontal cortex (PFC), and nucleus accumbens (NAc) core and shell separately in ethanol-exposed group as compared to naïve non-ethanol-exposed group. We then tested whether ceftriaxone would affect both GLT1 and ENT1 levels in these brain regions. P rats were given 24-hour concurrent access to 15% and 30% ethanol, water, and food for five weeks. On Week 6, P rats received 100 mg/kg ceftriaxone (i.p.) or a saline vehicle for five consecutive days. Ethanol consumption was measured daily for 8 days starting on Day 1 of injections. The naïve control group was exposed only to water and food. Statistical analyses revealed a significant reduction in daily ethanol consumption, starting on Day 2 of injections, for both ceftriaxonetreated groups as compared to saline-treated group. Alternatively, there were significant increases in water intake in ceftriaxone-treated groups as compared to saline group. There was no significant difference in body weight among all groups. Examination of GLT1 levels using Western blot in all groups showed downregulation of GLT1 expression in NAc core and NAc shell separately, but not in the prefrontal cortex (PFC). Importantly, ceftriaxone administration upregulates GLT1 level as compared to saline-treated ethanol-exposed group in NAc core, NAc shell, and PFC. Alternatively, using binding assay, we found that ENT1 was found significantly down-regulated in PFC; however, it was upregulated in NAc core and shell. Importantly, ceftriaxone did overcome the changes in ENT1 level only in the NAc core. These findings provide information about the regulatory effects of ceftriaxone of both GLT1 and ENT1 proteins in reduction of ethanol intake.