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Endogenous dynorphin in emotional control and stress response revisited


We recently demonstrated a clearly anxiolytic phenotype of prodynorphin-deficient (dynKO) mice on the C57bl/6N background. However, other groups observed a less prominent and partially paradigm-dependent anxiogenic phenotype or even anxiogenic phenotype of other dynKO mice. Therefore we backcrossed our dynKO mice onto the balb/c background and evaluated their anxiety-related behaviour.


In this study, we investigated anxiety and stress-related behaviour of germ-line prodynorphin knockout (dynKO) mice. Behavioural data were complemented by measurement of corticosterone serum levels.


Male dynKO mice exhibited about 2-fold ambulation in the open field center and intermediate areas. DynKO mice showed also longer distance travelled (2-fold) and more time spent on open arms of the elevated plus maze test. Significantly higher numbers of mice entering the open lit area in the light-dark test were observed in dynKO as compared to wild-type mice. As observed on the C57bl/6N background, only minor changes were observed in the stress-coping abilities measured in the tail suspension and forced swim tests. A reduction of basal corticosterone levels was observed in dyn-KO mice.


Taken together our data support the anxiogenic effects of endogenous dynorphin as observed on the C57bl/6N background. However, the phenotype is less clear on the balb/c background.


This project was supported by the Austrian Science Fund (P20107).

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Correspondence to Christoph Schwarzer.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Schwarzer, C., Lutsch, C., Schunk, E. et al. Endogenous dynorphin in emotional control and stress response revisited. BMC Pharmacol 10, A32 (2010).

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  • Corticosterone Level
  • Field Center
  • Maze Test
  • Emotional Control
  • Corticosterone Serum