Ceftriaxone, a beta-lactam antibiotic, attenuates relapse-like ethanol-drinking behavior in alcohol-preferring rats

Abstract

Relapse-like ethanol-drinking behavior depends on increased glutamate transmission in the mesocorticolimbic motive circuit. Extracellular glutamate is regulated by a number of glutamate transporters. Of these transporters, glutamate transporter 1 (GLT1) is responsible for the majority of extracellular glutamate uptake. We have recently reported that ceftriaxone (CEF) treatment (i.p.), a β-lactam antibiotic known to elevate GTL1 expression, reduced ethanol intake in male alcohol-preferring (P) rats. We investigated here whether CEF treatment attenuates relapse-like ethanol-drinking behavior. P rats were exposed to free choice of 15% and 30% ethanol for 5 weeks and treated with CEF (50 and 100 mg/kg, i.p.) during the last 5 days of the 2-week deprivation period. Rats treated with CEF during the deprivation period showed a reduction in ethanol intake compared with saline-treated rats upon re-exposure to ethanol; this effect persisted for 9 days. Moreover, CEF-mediated attenuation in relapse to ethanol-drinking behavior was associated with upregulation of GLT1 level in prefrontal cortex and nucleus accumbens core. GLT1 upregulation was revealed only at the higher dose of CEF. In addition, CEF has no effect on relapse-like sucrose-drinking behavior. These findings suggest that ceftriaxone might be used as a potential therapeutic treatment for the attenuation of relapse-like ethanol-drinking behavior.

Keywords: EAAT2; Relapse; alcohol dependence; ethanol intake; glutamate.

Figure 1

A) Daily ethanol intake of male P rats for nine days of ethanol re-exposure, following five days of treatment during relapse period with saline (n = 8), CEF 50 mg/kg (n = 8) and CEF 100 mg/kg (n = 8). The graph represents average daily ethanol intake during the 9 days of ethanol re-exposure. The baseline values correspond to the average ethanol intake across the last 2 weeks of 5-week ethanol exposure. A one-way ANOVA, followed by a Dunnett post-hoc test, revealed a significant reduction in average daily ethanol consumption during the duration of re-exposure to ethanol for both CEF-treated groups as compared with the saline-treated group. B) Daily water intake of male P rats for 9 days of relapse paradigm, following 5 days of treatment with saline (n = 8), CEF 50 mg/kg (n = 8), or CEF 100 mg/kg (n = 8). The graph represents average daily water consumption during the 9 days of ethanol re-exposure. The baseline values correspond to the average water intake across the last 2 weeks of the 5-week ethanol exposure. A one-way ANOVA, followed by a Dunnett post-hoc test, revealed a significant increase in average daily water consumption during the duration of re-exposure to ethanol for both CEF-treated groups as compared to the saline-treated group. Values shown as means ± SEM. * p < 0.001 (A) and * p < 0.05 (B) depict a significant difference across doses for each day.

Figure 2

A) Daily body weight measurement of male P rats for 9 days, following 5 days of treatment with saline (n = 8), CEF 50 mg/kg (n = 8), or CEF 100 mg/kg (n = 8). The graph represents average daily body weight during the 9 days of ethanol re-exposure. A one-way ANOVA, followed by a Dunnett post-hoc test, demonstrated no significant effect of dose and day during the duration of re-exposure for all groups. B) Daily sucrose (10%) intake of male P rats for 9 days, following 5 days of treatment with saline (n = 4), CEF 50 mg/kg (n = 5), or CEF 100 mg/kg (n = 5). The graph represents average daily sucrose (10%) consumption (±SEM) during the 9 days of sucrose (10%) re-exposure. While the Day main effect was significant (p < 0.001), neither the interaction by Day and Dose (treatment) (p = 1.00) nor the Dose main effect (p > 0.612) was significant. In addition, there were no significant differences in sucrose intake between the baseline and days of re-exposure to sucrose. Values shown as means ± SEM.

Figure 3

Effects of 50 mg/kg (CEF-50, n= 4), 100 mg/kg (CEF-100, n = 4) or saline treatment (n = 4) on GLT1 expression in the PFC. (Upper panel) Immunoblots for GLT1 expression and β-tubulin as a control loading protein. (Lower panel) Quantitative analysis of immunoblots demonstrated a significant increase in the % ratio GLT1/β-tubulin in CEF-100-treated groups compared with saline control (100% control-value) group. There was neither a significant difference between CEF-100 and CEF-50 groups nor between saline vehicle and CEF-50 groups. Values shown as means ± SEM. (* p < 0.05).

Figure 4

Effects of 50 mg/kg (CEF-50, n= 4), 100 mg/kg (CEF-100, n = 4) or saline treatment (n = 4) on GLT1 expression in the NAc core. (Upper panel) Immunoblots for GLT1 expression, and β-tubulin as a control loading protein. (Lower panel) Quantitative analysis of immunoblots demonstrated a significant increase in the ratio of GLT1/β-tubulin in CEF-100 treated group as compared with CEF-50 and saline control (100% control-value) groups. There was no significant difference between saline vehicle and CEF-50 groups. Values shown as means ± SEM. (* p < 0.05; ** p < 0.01).