Background: Outcomes of neurobehavioral studies are invariably affected by the variations in the anxiety traits of animals in the same species. Identifying those traits and categorizing them accordingly would improve the reproducibility of results, and reduce the variation in the results from different laboratories. Purpose: The present study was done to identify the possible groups among the normal population of outbred adult male Wistar rats. Methods: Anxiety traits were measured in elevated plus maze (EPM) test and open field test (OFT). The various anxiety responses from these tests were subjected to exploratory factor and hierarchical cluster analyses. Different clusters thus derived were compared with each other. Results and Conclusion: In exploratory factorial analysis, 2 components, that is, anxiety and activity were derived from the EPM and OFT parameters. Cluster analysis of EPM parameters classified the rats into 3 groups “high anxiety and low activity”, “medium anxiety and high activity”, and “low anxiety and medium activity”. Whereas, cluster analysis on OFT parameters identified one more group namely “low anxiety and high activity”. The rats which came under the clusters formed from the EPM and OFT parameters were not identical. Moreover, EPM and OFT may be measuring different aspects of anxiety.

Keywords:
Anxiety traits, Wistar rats, Elevated plus maze, Open field test, Cluster analysis, Factor analysis
1.
Chesler EJ, Wilson SG, Lariviere WR, et al: Identification and ranking of genetic and laboratory environment factors influencing a behavioral trait, thermal nociception, via computational analysis of a large data archive. Neurosci Biobehav Rev 2002; 26: 907–923.
2.
Izidio G, Lopes D, Spricigo L Jr, Ramos A: Common variations in the pretest environment influence genotypic comparisons in models of anxiety. Genes Brain Behav 2005; 4: 412–419.
3.
Crabbe JC, Wahlsten D, Dudek BC: Genetics of mouse behavior: interactions with laboratory environment. Science 1999; 284: 1670–1672.
4.
Steimer T: The biology of fear-and anxiety-related behaviors. Dialogues Clin Neurosci 2002; 4: 231–249.
5.
Gottesman II, Gould TD: The endophenotype concept in psychiatry: etymology and strategic intentions. Am J Psychiatry 2003; 160: 636–645.
6.
Litvin Y, Pentkowski NS, Pobbe RL, et al: Unconditioned models of fear and anxiety. Handbook of Behavioral Neurosci 2008; 17: 81–99.
7.
Sahgal A: Behavioural Neuroscience. A Practical Approach. Oxford, UK, Oxford University Press, 1993.
8.
Pellow S, Chopin P, File SE, 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.
9.
Rao RM, Sadananda M: Influence of state and/or trait anxieties of Wistar rats in an anxiety paradigm. Ann Neurosci 2016; 23: 44–50.
10.
Walf AA, Frye CA: The use of the elevated plus maze as an assay of anxiety-related behavior in rodents. Nat Protoc 2007; 2: 322–328.
11.
Landgraf R, Wigger A: Born to be anxious: neuroendocrine and genetic correlates of trait anxiety in HAB rats. Stress 2003; 6: 111–119.
12.
Prut L, Belzung C: The open field as a paradigm to measure the effects of drugs on anxiety-like behaviors: a review. Eur J Pharmacol 2003; 463: 3–33.
13.
Tabachnick BG, Fidell LS: Using Multivariate Statistics (ed 5). Boston, MA, Allyn & Bacon, 2007.
14.
O’connor BP: SPSS and SAS programs for determining the number of components using parallel analysis and Velicer’s MAP test. Behav Res Methods Instrum Comput 2000; 32: 396–402.
15.
Sosulina L, Meis S, Seifert G, et al: Classification of projection neurons and interneurons in the rat lateral amygdala based upon cluster analysis. Mol Cell Neurosci 2006; 33: 57–67.
16.
Yim O, Ramdeen KT: Hierarchical cluster analysis: comparison of three linkage measures and application to psychological data. Tutor Quant Methods Psychol 2015; 11: 8–21.
17.
File SE: The biological basis of anxiety; in Meltzer HY, Nerrozzi D (eds): Current Practices and Future Developments in the Pharmacotherapy of Mental Disorders. Amsterdam, Elsevier, 1991.
18.
Trullas R, Skolnick P: Differences in fear motivated behaviors among inbred mouse strains. Psychopharmacology (Berl) 1993; 111: 323–331.
19.
Castro JE, Diessler S, Varea E, et al: Personality traits in rats predict vulnerability and resilience to developing stress-induced depression-like behaviors, HPA axis hyper-reactivity and brain changes in pERK1/2 activity. Psychoneuroendocrinology 2012; 37: 1209–1223.
20.
Muigg P, Scheiber S, Salchner P, et al: Differential stress-induced neuronal activation patterns in mouse lines selectively bred for high, normal or low anxiety. PLoS One 2009; 4:e5346.
21.
Cruz AdM, Frei F, Graeff F: Ethopharmacological analysis of rat behavior on the elevated plus-maze. Pharmacol Biochem Behav 1994; 49: 171–176.
22.
Ohl F, Roedel A, Binder E, Holsboer F: Impact of high and low anxiety on cognitive performance in a modified hole board test in C57BL/6 and DBA/2 mice. Eur J Neurosci 2003; 17: 128–136.
23.
Goes TC, Antunes FD, Teixeira-Silva F: Environmental enrichment for adult rats: effects on trait and state anxiety. Neurosci Lett 2015; 584: 93–96.
24.
Correia D, Ribeiro AF, Godard AL, Boerngen-Lacerda R: Trait anxiety and ethanol: anxiolysis in high-anxiety mice and no relation to intake behavior in an addiction model. Prog Neuropsychopharmacol Biol Psychiatry 2009; 33: 880–888.
25.
Southwick SM, Vythilingam M, Charney DS: The psychobiology of depression and resilience to stress: implications for prevention and treatment. Annu Rev Clin Psychol 2005; 1: 255–291.
26.
Feder A, Nestler EJ, Charney DS: Psychobiology and molecular genetics of resilience. Nature Rev Neurosci 2009; 10: 446–457.
© 2018 S. Karger AG, Basel
2018
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.