Morphine withdrawal increases metabotropic glutamate 2/3 receptors expression in nucleus accumbens

Abstract

We examined the effects of chronic morphine treatment and withdrawal on the expression of metabotropic glutamate (mGlu)1, mGlu5, and mGlu2/3 receptors in the nucleus accumbens and caudate putamen. Rats received a 14-day morphine treatment (escalating doses from 10 to 140 mg/kg). Receptor density was evaluated after chronic treatment and after 1, 3, and 14 days of withdrawal. mGlu1 and mGlu5 expression in the nucleus accumbens and in the caudate putamen was not affected by any of the experimental manipulations. In contrast, mGlu2/3 receptors in the nucleus accumbens, but not in the caudate putamen, increased at day 1, 3, and 14 of withdrawal. We suggest that an increased expression of mGlu2/3 receptors in the nucleus accumbens might contribute to the symptoms of morphine withdrawal.

The role of glutamate and its receptors in mesocorticolimbic dopaminergic regions in opioid addiction

“…Agonists of group II mGluRs inhibited morphine withdrawal behaviors in 7-, 14-and 21-dayold rats (Zhu and Barr, 2004). The mGlu2/3 receptors in the NAc increased at days 1, 3, and 14 of morphine withdrawal (Modafferi et al, 2008). However, there were some conflicting reports.…”

Morphine Withdrawal Modifies Prion Protein Expression in Rat Hippocampus

“…Morphine hydrochloride (SALARS, Como, Italy) was dissolved in saline and administered twice daily (at 8am and 8pm) for 14 days, as previously described [39,40]. Briefly, the initial dose administered was 10 mg/kg and it was increased by 20 mg/kg every other day until the 14th day of treatment.…”