Rationale: Several studies have demonstrated a correlation between extracellular glutamate concentration in the mesolimbic reward pathway and alcohol craving. Extracellular glutamate concentration is regulated by several glutamate transporters. Glial glutamate transporter 1 (GLT1) is one of them that regulates the majority of extracellular glutamate concentration. In addition, cystine/glutamate antiporter (xCT) is another transporter that regulates extracellular glutamate.
Objectives: We focus in this study to determine the effects of ceftriaxone, β-lactam antibiotic, on glial proteins such as GLT1 isoforms, xCT, glutamate aspartate transporter (GLAST), and several associated signaling pathways as well as ethanol intake in P rats. Additionally, to examine the onset of signaling pathways associated with GLT1 upregulation following ceftriaxone treatment, we tested 2- versus 5-day daily dosing of ceftriaxone.
Results: Ceftriaxone treatment (100 mg/kg), 2 and 5 days, resulted in about five fold reduction in ethanol intake by P rats. The reduction in ethanol intake was associated with significantly enhanced expression of GLT1, GLT1a, GLT1b, and xCT in the nucleus accumbens (NAc) and prefrontal cortex (PFC) of 5-day ceftriaxone-treated P rats. Two-day-treated P rats showed marked changes in expression of these glutamate transporters in the PFC but not in the NAc. Importantly, ceftriaxone-treated P rats (2 and 5 days) demonstrated enhanced phosphorylation of Akt and nuclear translocation of nuclear factor kappaB (NFκB) in the NAc and PFC compared to control animals.
Conclusions: These findings demonstrate that ceftriaxone treatment induced upregulation of GLT1, GLT1 isoforms, and xCT in association with activation of the Akt-NFκB signaling pathway.
Keywords: Ceftriaxone; EAAT2; GLT1; Glutamate; Nucleus accumbens; P rats; Prefrontal cortex.