RESUMEN
Objectives: To observe the drug seeking behavior in chronically morphine pretreated, abstinent rats and determine brain regions involved in this behavior. Methods: Preferences for morphine associated environments and Fos expression in some brain regions were measured 35 days after withdrawal of chronic morphine treatment. Results: The preference for the morphine environment was greatly increased by morphine pretreatment. The conditioned morphine pretreated group showed significantly higher Fos levels than either the conditioned or non conditioned control groups in the Cg, Ac C, BNST VL, ACE and ABL. Conclusions: A relationship between place preference behavior and neural indices of activation exist in the forebrain in response to morphine conditioned cues, which may be chronically modulated by prior morphine exposure.