The effects of lesion of the olfactory epithelium on morphine-induced sensitization and conditioned place preference in mice

Animals attain information about their environment through different sense organs. For example, the dominant external resource about the environment for rodents is obtained through olfaction. Many environmental conditions (stress or enriched environment) are known to affect an animal's susceptibility to drug addiction. However, it is not known how external information is integrated and paired with drug stimuli to develop into addictive behavior. Here, we investigated the effects of olfactory epithelium lesions induced with ZnSO4 effusion (ZnE) on morphine-induced sensitization and conditioned place preference in mice. We found that the lesion of the olfactory epithelium attenuated the repeated morphine (40 mg/kg)-induced behavioral sensitization and morphine-induced conditioned place preference (CPP) behaviors, such as hyper-locomotion during morphine (40 mg/kg) conditioned training. Additionally, the expression of FosB-like proteins, transcription factors associated with behavioral alterations, in the nucleus accumbens of the brain was attenuated in morphine administered mice treated by ZnE. Taken together, these results indicated that lesion of the olfactory epithelium lead to a decrease in morphine sensitization and CPP behavior in mice as well as modulate specific molecular markers of neuroadaption to drugs of abuse. These findings also suggest that olfaction plays an important role in the development of addictive behaviors that can be modulated by external actions. (C) 2012 Elsevier B.V. All rights reserved.