Social interaction: responses to chlordiazepoxide and the loss of isolation-reared effects with paired-housing

Abstract

This study investigated the action of chlordiazepoxide (CDP), on the social interaction (SI) of adult rats maintained in one of three housing conditions: (i) group-reared, (ii) isolated from weaning or (iii) paired during adulthood after initial isolation at weaning (pair-housed former isolates; PHFIs). Group-reared rats and PHFIs rats were housed in pairs starting 21 days prior to the first experiment. For these two groups, CDP (2.5 and 5.0 mg/kg) increased SI in unfamiliar, but not familiar (cagemate) pairings. In rats isolated throughout, SI was markedly increased and this was unaffected by CDP. Isolated rats also exhibited increased motor activity (MA) during SI tests, and the MA of both isolates and PHFIs was reduced by CDP. Finally, levels of aggression were very low except in isolates, where a relatively modest increase in aggression was reversed by either pairing or CDP. To summarise, isolation-induced increases in SI and aggression were reversed by pairing, but pairing only attenuated isolation-induced increases in MA. Although CDP reduced the elevated aggression and MA of isolated rats, it had no effect on their elevated SI scores. These data question the permanence of anxiety-related, isolation-induced behavioural changes and stand in contrast to the irreversible anxiogenic profile reported for isolation-reared rats in the elevated X-test.

Effects of two acute stressors on the anxiolytic efficacy of chlordiazepoxide

“…In the social interaction test, chlordiazepoxide decreased aggression both in rats reared in isolation and in rats reared in groups. However, social interaction was increased in group-reared rats only (Vale and Montgomery 1997). Wongwitdecha and Marsden (1996) obtained similar data.…”

Long-lasting recovery of psychotic-like symptoms in isolation-reared rats after chronic but not acute treatment with the cannabinoid antagonist AM251

“…First, we assessed the validity of the isolation-rearing protocol before performing other behavioural and neurochemical analyses. In fact, animals reared in isolation show a pattern of behavioural alterations such as hyperlocomotion in a novel environment (Bakshi & Geyer, 1999 ;Einon & Morgan, 1976) cognitive impairment (Bianchi et al 2006 ;Fone & Porkess, 2008 ;Hellemans et al 2004 ;Lapiz et al 2000 ;Lu et al 2003) and an increase in aggressive behaviours in the social interaction test (Toth et al 2008 ;Vale & Montgomery, 1997 ;Wongwitdecha & Marsden, 1996). In our study, after 5 wk of isolation rearing, rats presented a marked increase in total horizontal locomotor activity, a cognitive impairment in the NOR test and a significant increase in the number of aggressive behaviours.…”

Behavioural and neurochemical effects of post-weaning social isolation in rodents—Relevance to developmental neuropsychiatric disorders

“…An increase in social interaction occurs in male but not female Wistar rats following isolation rearing which is more evident when isolation begins on PND21 than PND30 (Ferdman et al, 2007). This increase in social interaction is particularly evident under conditions of bright light and may be largely due to an increase in aggressive behaviours (Vale and Montgomery, 1997;Wongwitdecha and Marsden, 1996c). A similar increase in aggressive behaviour is a prominent feature in mice reared in isolation ( Fig.…”