Anxiety-Like and Exploratory Behaviors of Isolation-Reared Mice in the Staircase Test

Abstract

Abstract. The behavior of isolation-reared mice has not yet been studied in the staircase test. The present study examined the effects of anxiolytic or anxiogenic agents and isolation rearing on the behavior of ddY (outbred) strain mice in the staircase test. Diazepam and phenobarbital increased the number of steps climbed, but did not affect rearing behavior in group-reared mice. FG-7142, a benzodiazepine inverse agonist, significantly increased the number of rearing with no changes in the number of steps climbed in group-reared mice. Methamphetamine increased the number of steps climbed and decreased the number of rearing in group-reared mice. Although isolation-reared mice showed hyperactivity, there was no difference in locomotor activity for the test period of 3 min between isolation-and group-reared mice. Under these conditions, isolation rearing increased the numbers of steps climbed and rearing compared to group-reared controls. Microanalysis of locomotor patterns of group-reared mice in the staircase test showed that anxiolytic drugs increased the number of climbing to the top step of the staircase and methamphetamine increased the number of climbing to the first to third step. These results suggest that isolation rearing causes an anxiety-like state with increased exploratory behavior in mice.

Role of Social Encounter-Induced Activation of Prefrontal Serotonergic Systems in the Abnormal Behaviors of Isolation-Reared Mice

“…All experiments were conducted on 9-week-old male or female mice. The isolated male ddY-strain mice showed abnormal behaviors (Ago et al, 2007(Ago et al, , 2012Sakaue et al, 2001Sakaue et al, , 2003 consistent with those in C57BL/6J or ICR strain mice (Ibi et (Tocris Cookson, Bristol, UK), and pentobarbital (Nacalai Tesque, Kyoto, Japan) were used in this study. Osemozotan and diazepam were suspended in 0.5% w/v carboxymethylcellulose.…”

“…The ddY outbred male or female mice (SHIMIZU Laboratory Supplies, Kyoto, Japan) were weaned at 3 weeks of age and divided equally and concurrently into isolation-and group-housed conditions. The isolated male and female mice were individually housed for 6 weeks in wire-topped opaque polypropylene cages (24 Â 17 Â 12 cm 3 ), whereas control male mice were housed in groups (5-6 per cage) in the same-sized wire-topped clear plastic cages (Ago et al, 2007Koda et al, 2008). All mice were housed under a standard 12-h light/dark cycle (lights on at 0800 hours) at a constant temperature of 22±1 1C, with free access to food and water throughout the experiments.…”

“…Being raised in social isolation from early in life causes abnormal behaviors in adulthood, such as hyperlocomotion, aggressive behavior, deficits of prepulse inhibition, cognitive impairments, decreased social contact, and depression-and anxiety-like behavior in rodents (Ago et al, 2007Fone and Porkess, 2008;Lukkes et al, 2009a, b;Zhao et al, 2009). Post-weaning social isolation is a useful model to study the effects of adverse early-life experiences on behavior and the neural mechanisms associated with isolation-induced changes in mood and anxiety (Lapiz et al, 2003;Lukkes et al, 2009c).…”

Preliminary Studies on the Behavioural Effects of the Methanol Extract of Leonotis Nepetifolia Linn Stem in Mice

“…The ability of LNS to decrease the number of rearings without affecting step climbing behaviour is suggestive of an anxiolytic effect. The further enhancement of exploratory behaviour by diazepam as observed in this study may be explained as likely due to an extension of the anti-anxiety properties of the drug that increased exploratory activity of the mice (Ago et al, 2007, Gnanasekar et al, 2014. The inability of LNS to also increase step climbing behaviour was probably as a result of the doses used or may reflect anxiolytic action via a different mechanism compared to that of the benzodiazepines.…”

“…This suggests that LNS does not produce marked CNS depression at the doses tested. The staircase test has been proven to be a relatively simple, reliable and efficient experiment for the screening of anxiolytic agents (Ago et al, 2007). LNS was found to decrease the number of rearings in the staircase test without altering the number of steps climbed.…”