Predator Odor Stressor, 2,3,5‐Trimethyl‐3‐Thiazoline (TMT): Assessment of Stress Reactive Behaviors During an Animal Model of Traumatic Stress in Rats

Abstract Animal models utilizing predator odor stress are important in understanding implications for post‐traumatic stress disorder. 2,5‐dihydro‐2,4,5‐trimethylthiazoline (TMT) has been used to measure stress reactive behaviors during TMT exposure, indicative of stress coping behaviors. In addition, long‐term consequences of stress including contextual‐induced stress memory, anxiety‐like and hyperarousal behaviors, and subsequent increases in alcohol self‐administration can also be examined after TMT exposure. In this article, we describe the TMT exposure protocol used in our lab and how we measure different stress‐reactive behaviors that rats engage in during the TMT exposure. Rats are placed in Plexiglass chambers that contain white bedding on the bottom of the chamber and a metal basket in the top right corner containing a filter paper that 10 µl of TMT is pipetted onto. During the 10 min exposure, rats can move around the chamber freely. Exposures are recorded by a video camera for later analysis. During TMT exposure, rats engage in a variety of stress‐reactive behaviors, including digging and immobility behavior. These are two distinctly different types of stress‐induced behavioral coping strategies to measure individual differences in stress responsivity. To examine individual differences, we group rats into TMT‐subgroups based on time spent engaging in digging or immobility behavior. We calculate a digging/immobility ratio score in which we divide the total time spent digging by the total time spent immobile. A cut‐off strategy is used such that rats with a criterion ratio score <1.0 are classified as TMT‐1 (i.e., low digging/high immobility; greater passive coping) and rats with a ratio score >1.0 are classified as TMT‐2 (i.e., high digging/low immobility; greater active coping). Here, we provide a detailed description of the TMT exposure protocol and step‐by‐step process in evaluation of stress‐reactive behaviors. © 2024 Wiley Periodicals LLC. Basic Protocol 1 : Predator odor stressor exposure using TMT Basic Protocol 2 : Description of stress‐reactive behaviors during TMT exposure and formation of TMT‐subgroups