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Enhanced Morphine Preference Following Prolonged Abstinence: Association with Increased Fos Expression

Summary: Enhanced Morphine Preference Following Prolonged
Abstinence: Association with Increased Fos Expression
in the Extended Amygdala
Glenda C Harris1
and Gary Aston-Jones*,1
Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA
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.
Neuropsychopharmacology (2003) 28, 292299. doi:10.1038/sj.npp.1300037


Source: Aston-Jones, Gary - Department of Neurosciences, Medical University of South Carolina


Collections: Biology and Medicine