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Behavioral and molecular analysis of nicotine-conditioned place preference in zebrafish.

Kedikian X, Faillace MP, Bernabeu R - PLoS ONE (2013)

Bottom Line: A counterbalanced nicotine-exposed control group did not show a significant preference shift, providing evidence that the preference shift in the nicotine-paired group was not due to a reduction of aversion for this compartment.The results suggested that zebrafish exposed to nicotine in an unfriendly environment can develop a preference for that initially aversive place, which is likely due to the rewarding effect of nicotine.Therefore, this model can be used to screen exogenous and endogenous molecules involved in nicotine-associated reward in vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Studies using mice and rats have demonstrated that nicotine induces a conditioned place preference (CPP), with more effective results obtained by using biased procedures. Zebrafish have also been used as a model system to identify factors influencing nicotine-associated reward by using an unbiased design. Here, we report that zebrafish exhibited putative nicotine biased CPP to an initially aversive compartment (nicotine-paired group). A counterbalanced nicotine-exposed control group did not show a significant preference shift, providing evidence that the preference shift in the nicotine-paired group was not due to a reduction of aversion for this compartment. Zebrafish preference was corroborated by behavioral analysis of several indicators of drug preference, such as time spent in the drug-paired side, number of entries to the drug-paired side, and distance traveled. These results provided strong evidence that zebrafish may actually develop a preference for nicotine, although the drug was administrated in an aversive place for the fish, which was further supported by molecular studies. Reverse transcription-quantitative real-time PCR analysis depicted a significant increase in the expression of α7 and α6 but not α4 and β2 subunits of the nicotinic receptor in nicotine-paired zebrafish brains. In contrast, zebrafish brains from the counterbalanced nicotine group showed no significant changes. Moreover, CREB phosphorylation, an indicator of neural activity, accompanied the acquisition of nicotine-CPP. Our studies offered an incremental value to the drug addiction field, because they further describe behavioral features of CPP to nicotine in zebrafish. The results suggested that zebrafish exposed to nicotine in an unfriendly environment can develop a preference for that initially aversive place, which is likely due to the rewarding effect of nicotine. Therefore, this model can be used to screen exogenous and endogenous molecules involved in nicotine-associated reward in vertebrates.

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Levels of pCREB protein in the zebrafish brain following nicotine-CPP.a) Western blot of pCREB in control and nicotine-paired zebrafish (CPP positive) that were euthanized 1.5 or 3 h following CPP test. b) Quantitative densitometry analysis of the positive band obtained in (a) expressed as a ratio relative to control zebrafish euthanized 1.5 h following CPP test. N = 6 per group, **p<0.01 Dunnett’s test after ANOVA.
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pone-0069453-g008: Levels of pCREB protein in the zebrafish brain following nicotine-CPP.a) Western blot of pCREB in control and nicotine-paired zebrafish (CPP positive) that were euthanized 1.5 or 3 h following CPP test. b) Quantitative densitometry analysis of the positive band obtained in (a) expressed as a ratio relative to control zebrafish euthanized 1.5 h following CPP test. N = 6 per group, **p<0.01 Dunnett’s test after ANOVA.

Mentions: We evaluated the levels of pCREB in control and CPP-positive zebrafish brain portions containing structures of the reward pathways. pCREB was selected considering that it has been described as a good marker for evaluating changes in neuronal activity in nicotine-treated animals [17], [36]. Because the phosphorylation of CREB is a transient mechanism, levels of pCREB were assessed 1.5 and 3 h following the CPP protocol and test. Figure 8 (a) shows an image of the blot obtained by using a specific antibody against CREB phosphorylated at serine 133 and (b) the quantification of band densities showed in (a). A significant increase in the level of pCREB was observed at 1.5 h after nicotine-CPP, but not at 3 h post-test (p<0.01) compared with saline control zebrafish.


Behavioral and molecular analysis of nicotine-conditioned place preference in zebrafish.

Kedikian X, Faillace MP, Bernabeu R - PLoS ONE (2013)

Levels of pCREB protein in the zebrafish brain following nicotine-CPP.a) Western blot of pCREB in control and nicotine-paired zebrafish (CPP positive) that were euthanized 1.5 or 3 h following CPP test. b) Quantitative densitometry analysis of the positive band obtained in (a) expressed as a ratio relative to control zebrafish euthanized 1.5 h following CPP test. N = 6 per group, **p<0.01 Dunnett’s test after ANOVA.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722213&req=5

pone-0069453-g008: Levels of pCREB protein in the zebrafish brain following nicotine-CPP.a) Western blot of pCREB in control and nicotine-paired zebrafish (CPP positive) that were euthanized 1.5 or 3 h following CPP test. b) Quantitative densitometry analysis of the positive band obtained in (a) expressed as a ratio relative to control zebrafish euthanized 1.5 h following CPP test. N = 6 per group, **p<0.01 Dunnett’s test after ANOVA.
Mentions: We evaluated the levels of pCREB in control and CPP-positive zebrafish brain portions containing structures of the reward pathways. pCREB was selected considering that it has been described as a good marker for evaluating changes in neuronal activity in nicotine-treated animals [17], [36]. Because the phosphorylation of CREB is a transient mechanism, levels of pCREB were assessed 1.5 and 3 h following the CPP protocol and test. Figure 8 (a) shows an image of the blot obtained by using a specific antibody against CREB phosphorylated at serine 133 and (b) the quantification of band densities showed in (a). A significant increase in the level of pCREB was observed at 1.5 h after nicotine-CPP, but not at 3 h post-test (p<0.01) compared with saline control zebrafish.

Bottom Line: A counterbalanced nicotine-exposed control group did not show a significant preference shift, providing evidence that the preference shift in the nicotine-paired group was not due to a reduction of aversion for this compartment.The results suggested that zebrafish exposed to nicotine in an unfriendly environment can develop a preference for that initially aversive place, which is likely due to the rewarding effect of nicotine.Therefore, this model can be used to screen exogenous and endogenous molecules involved in nicotine-associated reward in vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Studies using mice and rats have demonstrated that nicotine induces a conditioned place preference (CPP), with more effective results obtained by using biased procedures. Zebrafish have also been used as a model system to identify factors influencing nicotine-associated reward by using an unbiased design. Here, we report that zebrafish exhibited putative nicotine biased CPP to an initially aversive compartment (nicotine-paired group). A counterbalanced nicotine-exposed control group did not show a significant preference shift, providing evidence that the preference shift in the nicotine-paired group was not due to a reduction of aversion for this compartment. Zebrafish preference was corroborated by behavioral analysis of several indicators of drug preference, such as time spent in the drug-paired side, number of entries to the drug-paired side, and distance traveled. These results provided strong evidence that zebrafish may actually develop a preference for nicotine, although the drug was administrated in an aversive place for the fish, which was further supported by molecular studies. Reverse transcription-quantitative real-time PCR analysis depicted a significant increase in the expression of α7 and α6 but not α4 and β2 subunits of the nicotinic receptor in nicotine-paired zebrafish brains. In contrast, zebrafish brains from the counterbalanced nicotine group showed no significant changes. Moreover, CREB phosphorylation, an indicator of neural activity, accompanied the acquisition of nicotine-CPP. Our studies offered an incremental value to the drug addiction field, because they further describe behavioral features of CPP to nicotine in zebrafish. The results suggested that zebrafish exposed to nicotine in an unfriendly environment can develop a preference for that initially aversive place, which is likely due to the rewarding effect of nicotine. Therefore, this model can be used to screen exogenous and endogenous molecules involved in nicotine-associated reward in vertebrates.

Show MeSH
Related in: MedlinePlus