A rat model of psychopathology for use in exercise science

Exploratory behavior, defecation, urination, and a subjective psychophysical rating system were evaluated in a series of four experiments designed to assess rat psychopathology. In every case, individual rats were studied for 5-min periods in an open field consisting of 49 7.5-inch squares. We find that the open-field test can be scored in a highly objective manner (r = 0.93-0.98) by two observers. The reproducibility (r = 0.79-0.85) of the assessment using total squares traversed is not improved using any of the other parameters evaluated. Use of total squares alone was also found to be in agreement with a subjective behavioral rating procedure (r = 0.96-0.98). Fifty percent of overall variability occurs in a rat's first trial. Therefore, the average of total squares traversed on the second and third (not necessarily consecutive) days provides a reliable and objective index of a rat's emotional status. Using this criterion, we find that a random group of 30 adult, male Sprague-Dawley rats exhibit a range of psychopathologies. We propose that this method of assessment provides a rat model of emotionality which should theoretically be modifiable by experimental paradigms involving exercise and pharmacological or dietary intervention.