Effects of acute and repeated morphine treatment on κ-opioid receptor protein levels in mesocorticolimbic system

J Recept Signal Transduct Res. 2014 Feb;34(1):44-7. doi: 10.3109/10799893.2013.856919. Epub 2013 Nov 12.

Abstract

Context: Our previous study demonstrated that acute and repeated morphine treatment differentially regulated κ-opioid receptor mRNA levels in the rat mesocorticolimbic system. Here, we further investigated the effects of morphine on protein levels of κ-opioid receptor in this reward-related circuitry.

Methods: Three groups of rats received intraperitoneal injection of saline, acute morphine (8.0 mg/kg) and repeated morphine (8.0 mg/kg, once daily for 5 consecutive days) and the κ-receptor protein expression was examined by Western blot analysis.

Results: We found that acute morphine treatment did not affect the κ-receptor protein levels in medial prefrontal cortex (mPFC), nucleus accumbens (NAc) and ventral tegmental area (VTA). However, repeated morphine treatment downregulated the κ-receptor protein levels in mPFC and VTA, while there was no significant change in NAc.

Conclusions: These results, along with those reported previously, suggested that morphine dependence may be associated with regionally specific changes in κ-opioid receptor expression in mesocorticolimbic system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Gene Expression Regulation / drug effects
  • Humans
  • Morphine / administration & dosage*
  • Prefrontal Cortex / drug effects
  • RNA, Messenger / drug effects*
  • Rats
  • Receptors, Opioid, kappa / biosynthesis*
  • Ventral Tegmental Area / drug effects

Substances

  • RNA, Messenger
  • Receptors, Opioid, kappa
  • Morphine