Role of suppressing GLT-1 and xCT in ceftriaxone-induced attenuation of relapse-like alcohol drinking in alcohol-preferring rats

Alcohol dependence results in long-lasting neuroadaptive changes in meso-corticolimbic system, especially in the nucleus accumbens (NAc), which drives relapse-like ethanol drinking upon abstinence or withdrawal. Within NAc, altered glutamate homeostasis is one of the neuroadaptive changes caused by alcohol dependence. Accumbal glutamate homeostasis is tightly maintained through glutamate transporter 1 (GLT-1) and cystine-glutamate antiporter (xCT). But the role of GLT-1 and xCT in relapse-like ethanol drinking is poorly understood. Here, we used alcohol-preferring (P) rats in relapse-like ethanol drinking paradigm to (a) determine the effect of relapse-like ethanol drinking on gene and protein expression of GLT-1 and xCT in NAc, measured by quantitative polymerase chain reaction (qPCR) and Western blot, respectively; (b) examine if glutamate uptake is affected by relapse-like ethanol drinking in NAc, measured by radioactive glutamate uptake assay; (c) elucidate if upregulation of either/both GLT-1 or/and xCT through ceftriaxone is/are required to attenuate relapse-like ethanol drinking. The GLT-1 or xCT protein expression was suppressed during ceftriaxone treatments through microinjection of GLT-1/xCT anti-sense vivo-morpholinos. We found that relapse-like ethanol drinking did not affect the gene and protein expression of GLT-1 and xCT in NAc. The glutamate uptake was also unaltered. Ceftriaxone (200 mg/kg body weight, i.p.) treatments during the last 5 days of abstinence attenuated relapse-like ethanol drinking. The suppression of GLT-1 or xCT expression prevented the ceftriaxone-induced attenuation of relapse-like ethanol drinking. These findings confirm that upregulation of both GLT-1 and xCT within NAc is crucial for ceftriaxone-mediated attenuation of relapse-like ethanol drinking.