Sex Differences In Avoidance Extinction After Contextual Fear Conditioning: Anxioescapic Behavior In Female Rats

Fear memories are important for survival and are implicated in the etiology of fear disorders such as Post Traumatic Stress Disorder (PTSD). Fear memories are well studied pre-clinically and sex differences in rodent fear expression have been reported: females tend to freeze less than males. Whether this is a difference in fear learning or expression is debated. We aimed to differentiate between these possibilities with a task that allowed female rats to express fear memory by moving, rather than freezing. We assessed fear extinction after contextual fear conditioning in the isolated Shock Arm of a Y-maze in female and male rats by either placing them back in the isolated Shock Arm (Fear Extinction in the Shock Context) or allowing them to move freely in the Y-maze during extinction training and enter/avoid the Shock Arm (Avoidance Extinction). We confirmed that female rats freeze less than males during fear extinction in both settings. During Avoidance Extinction, however, both sexes had similar avoidance of the Shock Context, showing comparable fear memory and extinction. Additionally, female rats made more entries into the non-shock arms. Thus, female and male rats have similar fear learning but females express it with an active motor response. Furthermore, female rats also exhibited an active motor response under other anxiogenic conditions (Elevated Plus Maze) and had higher reactivity (Acoustic Startle Response) but not when fear-eliciting stimuli were present: cat hair and foot-shock. In summary, female rats have an active motor response to anxiogenic stimuli which we termed 'Anxioescapic' behavior strategy. This article is part of a Special Issue entitled: In memory of Ivan Izquierdo South American pioneer of the Neuroscience of Memory Temporal dynamics and molecular mechanisms. (C) 2022 IBRO. Published by Elsevier Ltd. All rights reserved.

Automated summary

According to animal experiments, there are differences in the expression of fear memories between female and male rats. Female rats tend to express fear memories through active motor responses, which is referred to as "Anxioescapic" behavior strategy. There is no significant difference in fear learning between female and male rats.