Ceftriaxone upregulates the glutamate transporter in medial prefrontal cortex and blocks reinstatement of methamphetamine seeking in a condition place preference paradigm

Abstract

Glutamate signaling plays an essential role in drug-seeking behavior. Using reinstatement of conditioned place preference (CPP), we determined whether ceftriaxone, a β-lactam antibiotic known to increase the expression and activity of the glutamate transporter (EAAT₂) on glial cells, blocks methamphetamine-triggered reinstatement of CPP. Rats acquired methamphetamine CPP following 7 consecutive days of conditioning, during which each animal received pairings of alternating morning methamphetamine (2.5 mg/kg, IP) and afternoon saline (IP). Animals showing CPP were successfully extinguished with repeated twice daily saline administration over a 7-day period. Ceftriaxone (200 mg/kg, IP) was administered (vs. saline) once a day for 7 days during the extinction period. Upon successful extinction, animals received a single dose of methamphetamine (2.5 mg/kg, IP) for reinstatement and were tested for CPP one day later. Using real time PCR, EAAT₂ mRNA levels in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) were quantified in response to ceftriaxone. Ceftriaxone blocked methamphetamine-triggered reinstatement of CPP and significantly increased EAAT₂ mRNA levels in the mPFC, with a trend towards significance in the NAc. In conclusion, Ceftriaxone modulated the expression of the glutamate transporter in a critical region of the cortico-striatal addiction circuitry and attenuated drug-seeking behavior in rats. Further research is needed to test the efficacy of compounds targeting the EAAT₂ in human methamphetamine-dependent users.

Fig. 1

Acquisition (A), extinction (B) and reinstatement (C) of CPP in methamphetamine dependent rats assigned to ceftriaxone vs. saline groups (Ceftriaxone group recived ceftriaxone 200 mg/kg IP only during the extinction phase of the study). Time spent in methamphatmine-paired chamber during reinstatement (n=8) (mean±SEM): 12.83±0.74 vs. 4.14±0.5 two-tailed independent t-test=27.5, df=14, p<0.001.

Fig. 2

Ceftriaxone reduces the preference score (i.e. time spent in methamphetamine-paired/saline-paired chambers) during reinstatement: t(14)=3.450, p=0.0039.

Fig. 3

No effect of ceftriaxone on locomotor activity (n=8) (F=(0,98)=26.36, p<0.39).

Fig. 4

EAAT₂ mRNA concentration in (A) NAc (n=16) [F (1,14)=3.340, p<0.089] and (B) mPFC (n=16) [F (1,14)=7.101, p<0.018], in ceftriaxone+methamphetamine-treated (black columns) and saline+methamphetamine (clear columns) control groups at 4 h following the last ceftriaxone administered during simulated addiction (p<0.018).

Fig. 5

EAAT₂ mRNA concentration in (A) NAc [F (1,14)=2.14, p<0.31] (n=16) and (B) mPFC(n=16) [F (2,11)=5.955, p<0.018] in ceftriaxone+methamphetamine-treated (black columns) and saline+methamphetamine (clear columns) control groups at 72 h following the last ceftriaxone administered during extinction.