title: Serotonin depletion induces pessimistic-like behavior in a cognitive bias paradigm in pigs.
abstract: Cognitive and affective processes are highly interrelated. This has implications for neuropsychiatric disorders such as major depressive disorder in humans but also for the welfare of non-human animals. The brain serotonergic system might play a key role in mediating the relationship between cognitive functions and affective regulation. The aim of our study was to examine the influence of serotonin depletion on the affective state and cognitive processing in pigs, an important farm animal species but also a potential model species for biomedical research in humans. For this purpose, we modified a serotonin depletion model using para-chlorophenylalanine (pCPA) to decrease serotonin levels in brain areas involved in cognitive and affective processing (part 1). The consequences of serotonin depletion were then measured in two behavioral tests (part 2): the spatial judgement task (SJT), providing information about the effects of the affective state on cognitive processing, and the open field/novel object (OFNO) test, which measures behavioral reactions to novelty that are assumed to reflect affective state. In part 1, 40 pigs were treated with either pCPA or saline for six consecutive days. Serotonin levels were assessed in seven different brain regions 4, 5, 6, 11 and 13days after the first injection. Serotonin was significantly depleted in all analyzed brain regions up to 13days after the first application. In part 2, the pCPA model was applied to 48 animals in behavioral testing. Behavioral tests, the OFNO test and the SJT, were conducted both before and after pCPA/saline injections. While results from the OFNO tests were inconclusive, an effect of treatment as well as an effect of the phase (before and after treatment) was observed in the SJT. Animals treated with pCPA showed more pessimistic-like behavior, suggesting a more negative affective state due to serotonin depletion. Thus, our results confirm that the serotonergic system is a key player in cognitive-emotional processing. Hence, the serotonin depletion model and the spatial judgement task can increase our understanding of the basic mechanisms underlying both human neuropsychiatric disorders and animal welfare.
authors.affiliation: Institute of Behavioral Physiology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany.
authors.forename: Jenny
authors.initials: J
authors.lastname: Stracke
authors.affiliation: Institute of Behavioral Physiology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany.
authors.forename: Winfried
authors.initials: W
authors.lastname: Otten
authors.affiliation: Institute of Genetics and Biometry, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Tuchscherer
authors.affiliation: Institute of Behavioral Physiology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany; Behavioral Sciences, Faculty of Agricultural and Environmental Sciences, University of Rostock, D-18059 Rostock, Germany.
authors.forename: Birger
authors.initials: B
authors.lastname: Puppe
authors.affiliation: Institute of Behavioral Physiology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany. Electronic address: duepjan@fbn-dummerstorf.de.
authors.forename: Sandra
authors.initials: S
authors.lastname: Düpjan
mesh_terms: D000339:Affect / Q000187:drug effects / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D005106:Exploratory Behavior / Q000187:drug effects; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D007600:Judgment / Q000187:drug effects / Q000502:physiology; D000067657:Pessimism; D011930:Reaction Time / Q000187:drug effects; D012701:Serotonin / Q000172:deficiency*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013552:Swine; D013997:Time Factors
chemical_list: D012702:Serotonin Antagonists; D012701:Serotonin; D010134:Fenclonine
keywords: Animal welfare; Brain; Cognition; Emotion; Spatial judgement task