European Journal of Pharmacology, 178 (1990) 135-138 Elsevier 135 F_JP20586 Short communication Chronic handling modifies the anxio|yfic effect of di epam in the elevated p|us-maze Ros R. Brett and Judith A. Pratt Department of Physiology and Pharmacology, Universityof Strathclyde, GeorgeStreet. GlasgowGI 1XW, U.K. Received 12 October 1989, accepted 23 January 1990 Rats treated for 3 days with diazepam demonstrated a clear anxiolytic action of the drug as assessed in the elevated plus-maze. However, in a chronic experiment, tr~ which all rats were handled for 28 days, no anxiolytic effect of diazepam could be shown either in rats treated for 3 days or in those treated for 28 days. These results suggest that there is an interaction between handling and the anxiolytic effect of diazepam. Elevated plus-maze; Anxiety; Handling; Habituation; Diazepam; (Rat) 1. Introduction The elevated plu~-maze has been used as an animal model of anxiety and to assess the anxio- lytic and anxiogenic effects of drugs. It is based on work by Montgomery (1955) which showed that a novel stimulus induced both fear and ex- ploratory behaviour in rats, and that open, elevated maze alleys were more aversive than enclosed al- leys. The test in its present form was developed by Handley and Mithani (1984) and vafidated by Pellow et al. (1985). The apparatus consists of a plus-shaped maze with two open and two enclosed arms, which is elevated from the grounds. The ratio of entries into the open arms to the to:al number of arm entries, and the ratio of time spent in the open arms to total time spent in both types of arm are used as measures of anxiety. These measures are increased by anxiolytic and de- creased by anxiogenic drugs. Most of the valida- tion has involved drugs acting at the benzodi- Correspondence to: J.A. Pratt, Department of Physiologyand Pharmacology, University of Strathclyde, George Street, Glasgow G1 1XW, U.K. azepine (BZ) receptor. Anxiolytics, however, which act at 5-HT receptors do not necessarily give positive results in this test. The elevated plus-maze, then, appears to be a simple and useful test to investigate anx/olytic and anxiogenic effects of BZ-like substances. More- over this test exploits a more 'natural" an~ety situation than, for example, the Geller-Seifter con- flict test or the Vogel pun/shed drinking test. While this test has primarily been applied to the study of the acute effects of BZs, more recently investigators have used it to examine the chronic effects of these drugs. For example, File et al. (1987) have demonstrated tolerance to the an~o- lytic effect of chlordiazepoxide in the plus-maze after 20 days treatment. Fritz et al. (1986) have also reported tolerance to the anxiolytic effect of diazepam (DZP) in the plus-maze after 15 days, but this involved repeated testing at 7 day inter- vals, which may have influenced the results In our laboratory, preUminary experiments have indi- cated that with repeated testing at 7 day intervals the acute effect of DZP, as measured in the plus- maze, wanes. We now report that repeated han- dling may influence the anxiolytic action of DZP. This could be important in the interpretation of 0014-2999/90/$03.50 © 1990 ElsevierScience Publishers B.V. (Biomedical Division)