Exposing rats to the predator odor of trimethylthiazoline (TMT), obtained from the red fox, was compared to exposure to the novel control odor of citronella. In E)(periment 1, TMT produced defensive freezing and an analgesic reaction that was reversed by an opiate antagonist. In Experiment 2, TMT augmented response stereotypy induced by an amphetamine injection. In Experiment 3, TMT interfered with working memory during 30-s, but not O-s, delay trials of a spatial-alternation task. However, a larger amount of TMT disrupted performance during delay and no-delay trials. In Experiment 4, TMT impaired the recall of the location of a hidden platform in a Morris water maze, and a preexposure injection of a benzodiazepine agonist prevented this deficit. These findings and their implications are discussed in terms of research involving similar paradigms with other stressors.Exposure to laboratory stressors influences a wide range of behavioral and neurophysiological processes in rats. Historically, much of the classic research on stress in rodents has examined how aversive stimulation, such as painful electric shock, affects unlearned defensive responses, stressinduced analgesia, drug reactivity, learned responses, and more complex cognitive behaviors. Because many of the behavioral testing procedures designed to assess the influence of foot shock am similar to those used in the present research on the effects of exposing rats to a predator stimulus, a brief review of some of the specific findings of' these earlier studies is important for making possible interstressor comparisons.Electric shock has been found to be an ideal laboratory stressor because its intensity and duration can be easily and precisely controlled . Many studies have shown that exposure to foot shock results in flight or

No abstract