Introduction
Several experimental models have been used to study anxiety in the rat (Crawley 1981,Matsubara & Matsushita 1982, Pellow et al 1985). We wanted to study do some often used rat models of anxiety detect the same submodalities of anxiety. We also tested do the behavioral parameters which are thought to be a sign of animal anxiety correlate with parameters detecting general motor activity (Ericson et al 1991, Walsh & Cummings 1976) or depression (Porsolt et al 1979).
Methods
The behavior of 20 naive SD-rats were observed in five behavioral models: illuminated open-field, dark activity meter, elevated plus-maze, two-compartment exploratory test, and forced swimming test. Scores of observed behaviours were correlated with each other to find correlations between those parameters in these different tests which are thought to be measures of rodent anxiety.
Results
In the open-field and in the activity meter, rearing behaviours correlated with each other suggesting that this type of motor activity reflects the same phenomenon in these two tests directed to detect exploratory activity. Ambulation in the open-field or in the dark activity meter tests is not a direct measure of anxiety or depression. According to the ambulation scores, different animals are active in the light than in the dark. Anxiety-like behaviour detected by using the plus-maze test is not detectable by using the two compartment exploratory test or the inner segment ambulation scoring in the open field-test. Scoring of defecation failed to correlate with any of the parameters in the so called specific tests of rodent anxiety. Finally, depression-like behaviour in the rat can not be detected by using tests directed to detect anxiety or exploratory motor activity.
Conclusions
Our results suggest that different tests for studying animal anxiety may detect different subtypes of anxiety. Alternatively, some of these tests thought to be measures of animal anxiety detect anxiety poorly. Therefore, several types of tests should always be performed when studies concerning induction or reduction of anxiety are done in the rat.
References
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Crawley, J.N.1981. Pharmacol Biochem Behav 15, 695-699
Ericson, E. Samuelsson, J. & Ahlenius, S. 1991. J. Pharmacol Methods 25,111-122
Matsubara, K. & Matsushita, A.1982. Psychopharmacol 77,279-283
Pellow, S. Chopin, P. File, S.F. Briley, M.1985. J. Neurosci. Meth. 14,149-167
Porsolt, R.D. Bertin, A. Blavet, N. Deniel, M. & Jalfre, M. 1979. Eur. J. Pharmacol. 57. 201-210
Walsh, R.N. & Cummings, R.A. The open field test: a critical review. 1976. Psychol. Bull. 83, 482-504