Investigation of Changes in Anxiety and Learning Behavior During Oestrous Cycle in the Rat

Abstract

Objective: Ovarian steroids modulate brain mechanisms such as learning, memory and novel object recognition. However, the influence of oestrous cycle on the selection of behavioural strategies in response to novelty and to partial or complete fearful stimuli has not yet been studied. In this study, we aimed to show the effect of oestrous cycle on learning, memory and selection of coping strategies in the face of anxiety. Material and Methods: We examined novelty-induced anxiety responses in female Wistar rats during the oestrous cycle in the open-field test and during the presentation of fearful partial or whole cues during the passive avoidance (PA) apparatus test. The open-field and passive avoidance behaviours of rats were analyzed during three phases of the oestrous cycle- oestrus, pro-oestrus and dioestrous. Results: The female rat in pro-oestrus phase spent less time in the centre of the open field (p<0.001) and showed decreased locomotor activity and exploratory behaviour in the apparatus (p=0.003). In the passive avoidance test, freezing behaviour increased in the pro-oestrus phase compared with the oestrus and dioestrous phases (p<0.001). Conclusion: The results of this study showed that the phases of the oestrous cycle could affect cognitive performance and behavioural coping strategies with novel stimuli and fearful cues.