Abstract
Tolerance and physical dependence caused by chronic treatment of narcotics are good models to study basic neuronal plasticity. Activation of the NMDA subtype of the glutamate receptor has been implicated as an anti-opioid system in the development of morphine analgesic tolerance and dependence. The present study examines the specific role of the ε1 subunit of the NMDA receptor using mice lacking the gene encoding ε1 subunit of the NMDA receptor (GluRε1-/- mice). GluRε1-/- mice showed significant enhancement and prolongation of morphine anti-nociception, compared with wild-type GluRε1+/+ mice. GluRε1-/- mice also showed a marked loss of the analgesic tolerance after repeated morphine treatments. In C57BL/6J mice treated with chronic morphine after tolerance paradigm, the GluRε1 protein expression significantly increased in periaqueductal gray matter (PAG), ventral tegmental area (VTA) and nucleus accumbens (NAc), but not amygdala or hippocampus. The rescue of GluRε1 protein by electroporation into the PAG and VTA, but not NAc of GluRε1-/- mice significantly reversed morphine analgesic tolerance liability. Similar attempts were also performed in the naloxone-precipitated physical dependence paradigm. GluRε1-/- mice showed marked loss of typical withdrawal abstinence behaviors, and significant enhancement of GluRε1 protein expression was only observed in NAc by chronic morphine treatments after dependence paradigm. The rescue of GluRε1 protein by electroporation into the NAc of GluRε1-/- mice significantly reversed the loss of abstinence behaviors. These findings suggest that GluRε1 has locus-specific roles in the development of morphine analgesic tolerance and physical dependence.
Original language | English (US) |
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Pages (from-to) | 6529-6536 |
Number of pages | 8 |
Journal | Journal of Neuroscience |
Volume | 23 |
Issue number | 16 |
DOIs | |
State | Published - Jul 23 2003 |
Externally published | Yes |
Keywords
- KO mice
- Locus-specific rescue
- Morphine tolerance and dependence
- NMDA receptor
- Neuronal network
- ε1 subunit
ASJC Scopus subject areas
- General Neuroscience