Effectivity of acute antidepressant treatment is determined by the valence of cognitive judgment bias in rats

[Speaker] Rafal Rygula:1
[Co-author] Michal Rychlik:1, Robert Drozd:1
1:Institute of Pharmacology Polish Academy of Sciences, Poland

Background: Pessimistically biased judgment has been associated with the aetiology and recurrence of depressive disorder in humans. In the present studies we investigated if biased judgments, measured as stable and enduring behavioural traits (optimism/pessimism), could determine vulnerability of laboratory rats to acute antidepressant treatments.
Methods: For this, initially, in a series of ambiguous-cue interpretation tests, we identified animals displaying 'pessimistic' and 'optimistic' traits. Subsequently, we tested, in a fully randomized Latin-square design, how these traits interacted with sensitivity of rats to the effects of 5 different (agomelatine, escitalopram, mirtazapine, venlafaxine and clomipramine) antidepressant drugs. The effects of antidepressant treatments were measured in the probabilistic reversal-learning paradigm, which allowed assessing the sensitivity of animals to positive and negative feedback, and in the progressive ratio schedule of reinforcement paradigm, which allowed assessment of approach and avoidance motivation.
Results: We report significant differences between 'optimistic' and 'pessimistic' rats in vulnerability to antidepressant treatments in both applied behavioural paradigms.
Conclusions: The results of our studies are discussed in terms of neurobiological mechanisms of the observed effects and their possible implications for establishing novel ways of treatment based on previous cognitive assessments. Supported by the National Science Centre (UMO-2014/13/B/NZ4/00214)

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