Enhanced morphine preference following prolonged abstinence: association with increased Fos expression in the extended amygdala

Neuropsychopharmacology. 2003 Feb;28(2):292-9. doi: 10.1038/sj.npp.1300037.

Abstract

We previously found that chronically morphine-pretreated, abstinent rats show stronger preferences for morphine-associated environments than placebo-pretreated rats. Here we show that this increased preference persisted for at least 5 weeks after withdrawal of chronic morphine. To determine brain regions involved in this behavior, we examined neural activation (as indexed by Fos-like proteins) induced by a morphine-conditioned place preference test. Placebo-pretreated (P) morphine-conditioned rats showed significantly elevated Fos in the anterior cingulate cortex (Cg), nucleus accumbens core (Ac-C) and shell (Ac-S), ventral lateral and dorsal lateral bed nucleus of the stria terminialis (BNST-VL and -DL), and central and basolateral amygdala nuclei (ACE, ABL) when compared to nonconditioned P rats. Chronically morphine-pretreated (M) rats that exhibited enhanced morphine preference 5 weeks after morphine withdrawal showed significantly greater Fos in all the same areas except the BNST-DL relative to conditioned P or nonconditioned M rats. Place preference measures and Fos expression were positively correlated in the Cg and ABL, for conditioned P animals, and in the Cg, ABL and BNST-VL for conditioned M animals. These results indicate a relationship between place preference behavior and neural indices of activation in the forebrain in response to morphine-conditioned cues that may be chronically modulated by prior morphine exposure.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amygdala / metabolism*
  • Animals
  • Conditioning, Psychological / physiology
  • Gene Expression Regulation / physiology
  • Male
  • Morphine Dependence / metabolism*
  • Morphine Dependence / psychology
  • Proto-Oncogene Proteins c-fos / biosynthesis*
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Substance Withdrawal Syndrome / metabolism
  • Substance Withdrawal Syndrome / psychology

Substances

  • Proto-Oncogene Proteins c-fos