Small platform stress increases exploratory activity of mice in staircase test.
Small platform (SP) stress was induced by placing mice on small platforms (3.5 cm diameter) surrounded by water for 24 h. This model contains several factors of stress like rapid eye movement (REM) sleep deprivation, isolation, immobilization and falling into the water. The staircase test consisted of placing a mouse in an enclosed staircase with 5 steps and recording (1) the number of steps and (2) rearings made during 3 min. SP stress increased the exploratory activity of mice in the staircase test as evidenced by an increase in the number of steps and rearings made In control mice diazepam (0.25 and 0.5 mg/kg) induced an anxiolytic effect in the staircase test as evidenced by a decrease in the number of rearings without changes in the number of steps. In SP stressed mice the anxiolytic effect of diazepam was not seen and the sedative effect as evidenced by a decrease in the number of steps was more pronounced. Buspirone at a dose of 1.0 mg/kg did not have effect on the behaviour of control or SP stressed mice in the staircase test. To study possible diurnal variations the staircase test was carried out at 3 different times of a day (08:00, 14:00, 20:00) with control and SP stressed mice. The exploratory activity of control mice in the staircase test gradually increased from 08:00 to 20:00 as evidenced by an increased number of steps and rearings made. SP stress increased the exploratory activity of mice irrespective of the time of testing. In conclusion, on the basis of these data the authors can propose that SP stress increases the exploratory activity of mice in the staircase test and induces a hyposensitivity of mice to the anxiolytic effect of diazepam. The effect of SP stress on the behaviour of mice in the staircase test is not caused by the disruptance of diurnal rhythms.
Pokk
P
P
Department of Pharmacology, Faculty of Medicine, University of Tartu, Estonia. pokk@ut.ee
Väli
M
M
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology / Q000627:therapeutic use; D002065:Buspirone / Q000494:pharmacology / Q000627:therapeutic use; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology; D003975:Diazepam / Q000494:pharmacology / Q000627:therapeutic use; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D013312:Stress, Physiological / Q000188:drug therapy / Q000503:physiopathology* / Q000523:psychology
D014151:Anti-Anxiety Agents; D003975:Diazepam; D002065:Buspirone