Conditioned place avoidance in the planaria Schmidtea mediterranea: A pre-clinical invertebrate model of anxiety-related disorders

• Published in: Behavioural processes 2023-08, Vol.210, p.104894-104894, Article 104894
• Main Authors: Jordan, Liam, Alcalá, José A., Urcelay, Gonzalo P., Prados, Jose
• Format: Article
• Language: English
• Subjects: anxiety; automation; extinction; invertebrates; Schmidtea mediterranea
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/j.beproc.2023.104894

The objective of the present study was to develop a model of avoidance learning and its extinction in planarians (Schmidtea mediterranea). Based on previous experiments showing conditioned place preference, we developed a procedure to investigate conditioned place avoidance (CPA) using shock as an unconditioned stimulus (US) and an automated tracking system to record the animals’ behaviour. In Experiment 1, we assessed the unconditioned properties of different shock intensities by measuring post shock activity. In two subsequent experiments we investigated CPA using different designs, surfaces as conditioned stimuli (CSs; rough and smooth), and different US intensities (5 V and 10 V). In general, we observed the successful development of CPA. However, CPA was stronger with higher shock intensities, and we found that, in our preparation, a rough surface is best at entering into an association with the shock than a smooth surface. Finally, we also observed extinction of CPA. The evidence of CPA and its extinction in flatworms validates the planaria as a pre-clinical model for the study of avoidance learning, a hallmark of anxiety disorders. •Planarians are sensitive to different shock intensities.•Planarians shocked in a distinctive context develop conditioned place avoidance.•Context non-reinforced exposure results in extinction of the avoidance response.•Planarians can be used as an invertebrate model to study avoidance behaviour.