Chronic Physical Exercise Reduces Anxiety-Like Behavior In Rats

Abstract

While many individuals with anxiety disorders receive drug therapy, many do not respond or adversely respond to drugs. An alternative treatment, exercise, has been shown to relieve negative feelings and induce positive shifts in mood. The purpose of this study was to establish an animal model to specifically test the effects of chronic physical exercise on anxiety-related behaviors. Thirty-two male Sprague Dawley rats were divided into two groups: runners (R) and nonrunners (NR). Runners ran on a treadmill for 45 minutes a day, five days a week, for ten weeks at a moderate intensity. Nonrunners remained in their cages in the treadmill room during the running period and were handled for an equal amount of time. After ten weeks of training, two behavioral tests were administered including the elevated plus maze and open field tests. Results comparing R and NR showed higher responses by R in percent open arm time and center square time during the elevated plus maze test, as well as in number of entries into the center, number of rears, and lower fecal boli count during the open field test, p < 0.05. In addition, there were no differences in total activity levels between groups as indicated by similar closed arm entries in the elevated plus maze test and total lines crossed in the open field test. These results indicate that treadmill training reduces anxiety-like behaviors in two animal tests of anxiety, without a significant change in total activity levels. These data are in support of treadmill training as a model to test the anxiolytic effects of exercise.

Key words

Physical activity - elevated plus maze - open field - treadmill - animal model - rat

References

• 1 Armstrong R B, Laughlin M H. Blood flows within and among rat muscles as a function of time during high speed treadmill exercise.  J Physiol. 1983;  344 189-205
• 2 Carmack M A, Mertens R. Measuring commitment to running: a survey of runners attitudes and mental states.  J Sport Psychol. 1979;  1 25-42
• 3 Chaouloff F. Influence of physical exercise on 5-HT_1A receptor- and anxiety-related behaviours.  Neurosci Lett. 1994;  176 226-230
• 4 Cruz A P, Frei F, Graeff F G. Ethopharmacological analysis of rat behavior on the elevated plus maze.  Pharmacol Biochem Behav. 1994;  49 171-176
• 5 Dishman R K. Physical activity and mental health.  Encyclopedia of Mental Health. 1998;  3 171-188
• 6 Dishman R K, Dunn A L, Youngstedt S D, Davis JM, Burgess ML, Wilson SP, Wilson MA. Increased open field locomotion and decreased striatal GABA_A binding after activity wheel running.  Physiol Behav. 1996;  96 699-705
• 7 Dunn A L, Dishman R K. Exercise and the neurobiology of depression.  Exerc Sport Sci Rev. 1991;  19 41-98
• 8 Fernandes C, File S E. The influence of open arm ledges and maze experience in the elevated plus maze.  Pharmacol Biochem Behav. 1996;  54 31-40
• 9 File S E. Behavioural Detection of Anxiolytic Action. In: Elliott, JM Heal DJ, Marsen CA (eds) Experimental approaches to anxiety and depression. New York, Wiley 1992: 24-44
• 10 File S E. One-trial tolerance to the anxiolytic effects of chlordiazepoxide in the plus-maze.  Psychopharmacol. 1990;  100 281-282
• 11 File S E, Andrews N. Low but not high doses of buspirone reduce the anxiogenic effects of diazepam withdrawal. Psychopharmacol.  1991;  105 578-582
• 12 Green S. Benzodiazepines, putative anxiolytics and animal models of anxiety.  TINS. 1991;  14 101-104
• 13 Handly S L, McBlane J W. An assessment of the elevated X-maze for studying anxiety and anxiety-modulating drugs.  J Pharmacol Toxicol Methods. 1993;  29 129-138
• 14 Jones N, King S M. Influence of circadian phase and test illumination on pre-clinical models of anxiety.  Physiol Behav. 2001;  72 99-106
• 15 Kang W, Wilson M A, Wilson S P. Overexpression of proenkephalin in the amygdala potentiates the anxiolytic effects of benzodiazepines.  Neuropsychopharmacology. 2000;  22 77-88
• 16 Long B C, van Stavel R. Effects or exercise training on anxiety. A meta-analysis.  J Appl Sport Psychol. 1995;  7 167-189
• 17 Pellow S. Anxiolytic and anxiogenic drug effects in a novel test of anxiety: Are exploratory models of anxiety in rodents valid?.  Methods Find Exp Clin Pharmacol. 1996;  8 557-565
• 18 Pellow S, Chopin P, File S E, Briley M. Validation of open:closed arm entries in an elevated plus-maze as a measure of anxiety in the rat.  J Neurosci Methods. 1985;  14 149-167
• 19 Royce J T. On the construct validity of open field measures. Psychol.  Bull. 1977;  84 1098-1106
• 20 Sarbadhikari S N, Dey S, Ray A K. Chronic exercise alters EEG power spectra in an animal model of depression.  Indian J Physiol Pharmacol. 1996;  40 47-57
• 21 Stock H S, Ford K, Wilson MA. Gender and gonadal hormone effects in the olfactory bulbectomy animal model of depression.  Pharmacol Biochem Behav. 2000;  67 183-191
• 22 Tharp G D, Carson W H. Emotionality changes in rats following chronic exercise.  Med Sci Sports Exerc. 1975;  7 123-126
• 23 Walsh R N, Cummins R A. The open-field test: a critical review.  Psychol Bull. 1976;  83 482-504
• 24 Weber J C, Lee R A. Effects of differing prepuberty exercise programs on the emotionality of male albino rats.  Res Quart . 1968;  39 748-751