Effect of acute predator stress on learning and memory in a zebrafish model

Abstract

Background: In zebrafish, the stress system is represented by the hypothalamo–pituitary–interrenal axis which is similar to human HPA axis. Several studies have reported that stress affects the learning and memory in humans and rodents. Like humans, zebrafish form spatial memories and its cholinergic system is involved in learning and memory. In one study, it has been reported that exposing zebrafish to its natural predator stress (Indian Leaf Fish) has resulted in significant behavioral response. Therefore, here, we propose this study to model learning and memory in zebrafish using predator stress. Aims and Objectives: The study aims to model learning and memory in zebrafish using predator stress and evaluate the influence of predator stress on learning and memory in zebrafish. Materials and Methods: 12 adult zebrafishes (Danio rerio) were divided into two groups: Stress group (n = 6) and control group (n = 6). Fish in the stress group individually was exposed to Indian leaf fish (predator stress) for 20 min (acute exposure) through live simulated video with audio intervention under completely closed environment without any entry of outside light source. Control group fish was not exposed to any stress. Plus maze learning session was conducted in both stress (before and after stress) and control fish, and short-term memory (STM) and long-term memory (LTM) were recorded. Results: Between day 1 and day 6 of training among the stress group and control group fishes, both showed a significant establishment of memory of the location of the food arm. The test group fishes showed significant changes in STM, immediately after exposure to the predator stress, but not in control group. LTM did not have any significant changes in both groups. Conclusion: Stress in the form of predator produced an acute change in STM established in these fishes. This effect in zebrafish observed could be effect of the traumatic event in the form of predator that the zebrafish is exposed to and that has resulted in an acute state of confusion and memory loss.