Placebo analgesia affects the behavioral despair tests and hormonal secretions in mice
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The placebo effect is a fascinating yet puzzling phenomenon, which has challenged investigators over the past 50 years. In previous studies, the investigators only focused on the placebo effect obtained within a single domain, and pain is the field in which most of the placebo research has been performed. However, recent research by our laboratory (Zhang and Luo in Psychophysiology 46:626–634, 2009; Zhang et al. 2011) showed that, in human subjects, the placebo effect can be transferred from one domain to the other, namely from pain to emotion.
The scope of this study was to investigate whether placebo analgesia could affect the depressive behavior in mice.
Materials and methods
Female C57/BL6 mice were trained to associate the context cue with elevated pain tolerance via a set of procedures. Then the forced swim test and tail suspension test were used to measure the depressive-like behaviors on the test day. Plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone were also detected.
Our results showed that the placebo analgesia, which was established by a set of procedures in mice, was transferable and could produce a significant antidepressant effect on depressive test. Plasma levels of corticosterone and ACTH further proved that the placebo analgesia that was established from pain-reducing training not only induced a significant placebo effect on pain, but also decreased significantly the hypothalamus–pituitary–adrenal axis (HPA) response to stress and produced a stress-alleviating effect.
These data show that placebo analgesia affects the behavioral despair tests and hormonal secretions in mice.
KeywordsPlacebo analgesia Depressive behavior Expectation Conditioning Mice
The authors would like to thank Professor Fabrizio Benedetti (University of Turin Medical School, Torino, Italy) for his review and helpful comments on this article. This work was supported by the project from the Key Laboratory of Mental Health, Chinese Academy of Sciences, Young Scientist project from IPCAS (08CX043004), National Hi-Tech Research and Development Program of China (grant nos. 2006AA02Z431, 2008AA021204, and 2008AA022604), National Natural Science Foundation of China (grant nos. 30800301, 30970890), Knowledge Innovation Program of the Chinese Academy of Sciences (grant nos. KSCX2-YW-R-28, KSCX2-YW-R-254, KSCX2-EW-Q-18, and KSCX2-EW-J-8), and National Basic Research Program of China (grant no. 2010CB833904).
- Marzouk HF, Zuyderwijk J, Uitterlinden P, van Koetsveld P, Blijd JJ, Abou-Hashim EM, el-Kannishy MH, de Jong FH, Lamberts SW (1991) Caffeine enhances the speed of the recovery of the hypothalamo-pituitary-adrenocortical axis after chronic prednisolone administration in the rat. Neuroendocrinology 54:439–446PubMedCrossRefGoogle Scholar