Placebo analgesia affects the behavioral despair tests and hormonal secretions in mice
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- Guo, JY., Yuan, XY., Sui, F. et al. Psychopharmacology (2011) 217: 83. doi:10.1007/s00213-011-2259-7
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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.