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 dorsallateral bed nucleus of the stria terminialis (BNST-VL and -DL), and centraland basolateralamygdala 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 allthe same areas except the BNST-DL relative to conditioned P ornonconditioned M rats. Place preference measures and Fos expression were positively correlated in the Cg and ABL, for conditioned Panimals, and in the Cg, ABL and BNST-VL for conditioned M animals. These results indicate a relationship between place preference behavior and neuralindices of activation in the forebrain in response to morphine-conditioned cues that may be chronically modulatedby prior morphine exposure.
All Science Journal Classification (ASJC) codes
- Psychiatry and Mental health
- Cingulate cortex
- Conditioned place preference
- Morphine dependence