Med. Weter. 68 (6), 376-379, 2012

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Nawrocka M, Kowalczyk M
Effects of 2-methyl-6-(phenylethyl)-pyridine (MPEP) – a selective mGluR5 receptor antagonist – on the behaviour of rats in an open field test in a situation of predicted inevitable stress
The aim of the work was to assess the effects of MPEP – a selective mGluR5 receptor antagonist with anti-anxiety properties – on the behaviour of rats in a situation of predicted and inevitable stress. Wistar rats kept under a reversed light-dark cycle (the light phase starting at 8 pm) were subjected to a stress procedure including immobilisation for two hours a day during five subsequent days. Prior to the first stress, tests were performed to evaluate general motor activity and activity in the central field (a fear response). On subsequent days the tests were repeated immediately before immobilisation at 24-hour intervals. After the last immobilisation, all animals were moved to their original cages. After a 48-hour break, the animals were divided into two groups: a control group, which received 0.9% NaCl (1 mL/kg i.p.), and a test group, which received MPEP (10 mg/1mL/kg i.p.) Sixty minutes after injections, examinations preceding the expected stress were repeated in the control and test groups. A four-day stress significantly reduced the total number of passages between fields and the activity in the central field compared with the situation prior to stress. A 48-hour break after the last stress situation resulted in a significant increase in general locomotor activity and activity in the central field in the control group. In the MPEP group, general locomotor activity was significantly reduced compared with the control group, and there was also an increased proportion of passages in the central field by comparison with the control group and with the baseline prior to a stress situation. The results of this study indicate that MPEP – an mGluR5 receptor antagonist with anti-anxiety properties – may prevent psychomotor excitation caused by a situation of predicted stress and may have anti-stress properties.
Key words: MPEP, inevitable stress, motor activity, rat.