title: Modelling affective pain in mice: Effects of inflammatory hypersensitivity on place escape/avoidance behaviour, anxiety and hedonic state.
abstract: BACKGROUND
  The place escape/avoidance paradigm (PEAP) has been used to assess the affective component of pain in rats. Using the Complete Freund's Adjuvant (CFA) model of inflammatory pain, the current study aimed at developing a mouse version of PEAP and investigating the relation between PEAP and other behavioural responses, namely anxiety-like behaviour, locomotor activity, and hedonic state.
  
  
  METHODS
  A novel paradigm assessing the affective component of pain in mice was developed by modifying the setup known from rat studies: Animals were forced to stay 2 × 5 min in the light and the dark area of a box while being stimulated with a suprathreshold filament on the untreated or treated paw, respectively. This was followed by a 30-min test with unrestricted movement. Anxiety-like behaviour, locomotor activity, and hedonic state were assessed with the elevated zero maze (EZM), an open field setup, and a saccharin preference test, respectively, and correlated with the PEAP behaviour to examine potentially confounding parameters of the novel paradigm.
  
  
  RESULTS
  In the PEAP, CFA-treated animals spent more time in the light area. CFA also increased anxiety-like behaviour significantly, whereas locomotor activity was unaffected. A significant, albeit modest, reduction in saccharin preference was observed. PEAP responses showed no significant correlations with any other behavioural measure.
  The PEAP results suggest that this paradigm might be successfully applied in mice to study affective pain. CFA treatment was associated with increased anxiety-like behaviour and anhedonia; however, this appeared unrelated to the PEAP responses.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark. Electronic address: louiserefsgaard@hotmail.com.
authors.forename: L K
authors.initials: LK
authors.lastname: Refsgaard
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Hoffmann-Petersen
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Sahlholt
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark.
authors.forename: D S
authors.initials: DS
authors.lastname: Pickering
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark.
authors.forename: J T
authors.initials: JT
authors.lastname: Andreasen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001008:Anxiety Disorders / Q000175:diagnosis / Q000209:etiology*; D001362:Avoidance Learning / Q000502:physiology*; D004195:Disease Models, Animal; D005260:Female; D005518:Food Preferences; D005620:Freund's Adjuvant / Q000633:toxicity; D006930:Hyperalgesia / Q000503:physiopathology; D007249:Inflammation / Q000139:chemically induced / Q000150:complications*; D008124:Locomotion / Q000187:drug effects / Q000502:physiology; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010146:Pain / Q000175:diagnosis / Q000209:etiology / Q000523:psychology; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D012439:Saccharin / Q000008:administration & dosage; D013549:Sweetening Agents / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D013549:Sweetening Agents; D005620:Freund's Adjuvant; D012439:Saccharin
keywords: Affective pain; Anhedonia; Anxiety; Avoidance behaviour; CFA