Open field

Abstract: Animal models have proven to be invaluable to researchers trying to answer questions regarding the mechanisms of behavior. The Open Field Maze is one of the most commonly used platforms to measure behaviors in animal models. It is a fast and relatively easy test that provides a variety of behavioral information ranging from general ambulatory ability to data regarding the emotionality of the subject animal. As it relates to rodent models, the procedure allows the study of different strains of mice or rats both laboratory bred and wild-captured. The technique also readily lends itself to the investigation of different pharmacological compounds for anxiolytic or anxiogenic effects. Here, a protocol for use of the open field maze to describe mouse behaviors is detailed and a simple analysis of general locomotor ability and anxiety-related emotional behaviors between two strains of C57BL/6 mice is performed. Briefly, using the described protocol we show Wild Type mice exhibited significantly less anxiety related behaviors than did age-matched Knock Out mice while both strains exhibited similar ambulatory ability.

Abstract: array of choices available for assaying this behavioral construct, and seeing that there are somewhat murky borders between the constructs ‘anxiety’, ‘fear’ and ‘depression’, he or she will explore the question further with an array of tests, after careful consideration of the idiosyncratic parameters required to elicit interpretable data from each test. Such attention to detail matters in real life, even when highly experienced behavioral-testing laboratories are involved. For example, three groups recently independently produced null mutant mice for the corticotropinreleasing hormone 2 receptor. Each group was obviously interested in testing the effects of this gene deletion on anxiety. The results were published as three back-to-back-to-back papers in Nature Genetics 1‐3 . All three groups tested both male and female mice on a version of the elevated plus-maze anxiety test and reported their reluctance to enter open arms of the maze, the accepted index of anxiety. One group found no difference between knockout and wild type of either sex; one group found greater anxiety in knockouts of both sexes; and the third found greater anxiety in male knockouts only. All three also used an open field test, where reluctance to enter the center of the apparatus was the index of anxiety. Again, three different results were reported: one group found a tendency for greater anxiety in null mutants of both sexes; one found significantly greater anxiety in null mutants; and the third found that null mutant males (but not females) spent significantly more time in the center of the field, but interpreted the result to indicate greater anxiety! The different results could derive from many sources, including: differences in animal husbandry and handling before testing; relatively subtle differences in the test apparatus and test protocols; the specific genetic constructs inserted into embryonic stem cells; the stem-cell source strain (three different substrains of 129 inbred mice were used that are known to vary genetically 4

Abstract: It is well known that the hypothalamo-pituitary-adrenal (HPA) axis is altered by early environmental experiences, particularly in the perinatal period. This may be one mechanism by which the environment changes the physiology of the animal such that individual differences in adult adaptative capabilities, such as behavioral reactivity and memory performance, are observable. To determine the origin of these behavioral individual differences, we have investigated whether the long-term influence of prenatal and postnatal experiences on emotional and cognitive behaviors in adult rats are correlated with changes in HPA activity. To this end, prenatal stress of rat dams during the last week of gestation and postnatal daily handling of rat pups during the first 3 weeks of life were used as two environmental manipulations. The behavioral reactivity of the adult offspring in response to novelty was evaluated using four different parameters: the number of visits to different arms in a Y-maze, the distance covered in an open field, the time spent in the corners of the open field, and the time spent in the open arms of an elevated plus-maze. Cognitive performance was assessed using a water maze and a two-trial memory test. Adult prenatally stressed rats showed high anxiety-like behavior, expressed as an escape behavior to novelty correlated with high secretion of corticosterone in response to stress, whereas adult handled rats exhibited low anxiety-like behavior, expressed as high exploratory behavior correlated with low secretion of corticosterone in response to stress. On the other hand, neither prenatal stress nor handling changed spatial learning or memory performance. Taken together, these results suggest that individual differences in adult emotional status may be governed by early environmental factors; however, perinatal experiences are not effective in influencing adult memory capacity.