Effects of rearing in different environments on subsequent environmental preference in rats

Abstract

Environmental preference of male rats reared during 2 months after weaning either in a complex and changing environment (EC) or in empty laboratory cages (SC) was assessed in 4 different experiments. For 2 weeks after differential rearing, rats were placed in groups of 6 in testing cages which were divided into 2 compartments with communicating holes. One of these compartments was empty; the other contained 6 objects (complex compartment). Daily, 3 objects were moved from 1 compartment to the other and replaced by new ones. The preference for any of the compartments was chiefly assessed by the localization of feces (Experiments I and II) and directly by the localization of the animals through videorecording (Experiments III and IV). Both EC and SC rats showed a significant preference for the empty compartment during both light and dark portions of the daily cycle, but particularly during the light portion.Moreover, EC and SC animals differed from one another in that the SC rats showed a stronger preferences for the empty compartment than the EC rats, especially when active. General preference for the empty compartment seemed to diminish slowly, but EC and SC rats tended to remain distinct in habitat selection, at least during the period tested. This behavioral difference, tentatively interpreted in terms of neophobia, might constitute a possible mechanism for automaintenance of differential rearing effects.

Persistence of visual cortex dendritic alterations induced by postweaning exposure to a "superenriched" environment in rats.

“…In a factorial analysis of initial experience condition by age of subject, the consistent presence of experience effects combined with the relatively rare appearance of either age effects or interactions indicated that the dominant result was for the dendritic effects of the initial superenriched environment exposure to persist through the subsequent period of individual housing.Although it has been known for some time that various regions of the neocortex exhibit altered dendritic morphology in response to exposure to a complex environment (Greenough & Volkmar, 1973), the degree to which these dendritic effects persist is unknown. Exposure of rodents to a complex environment (EC) also results in significant changes in behavior relative to animals housed individually (1C) or socially in standard caging (e.g., Hebb, 1947;Will, Pallaud, Ungerer, & Ropartz, 1979; see Greenough, 1976, for review), brain chemistry, and brain size and weight (e.g., Diamond, 1967;Rosenzweig, Bennett, & Diamond, 1972). The relative permanence of some of these environmentally induced changes has been examined by switching animals between the complex environment and individual housing.…”

“…Although it has been known for some time that various regions of the neocortex exhibit altered dendritic morphology in response to exposure to a complex environment (Greenough & Volkmar, 1973), the degree to which these dendritic effects persist is unknown. Exposure of rodents to a complex environment (EC) also results in significant changes in behavior relative to animals housed individually (IC) or socially in standard caging (e.g., Hebb, 1947; Will, Pallaud, Ungerer, & Ropartz, 1979; see Greenough, 1976, for review), brain chemistry, and brain size and weight (e.g., Diamond, 1967; Rosenzweig, Bennett, & Diamond, 1972). The relative permanence of some of these environmentally induced changes has been examined by switching animals between the complex environment and individual housing.…”

Conventional laboratory housing increases morbidity and mortality in research rodents: results of a meta-analysis

“…We extracted details of which resources (substrates, items or structures) were included in both housing types. Further, we extracted data on factors likely to compromise EH effectiveness (determined a priori: see pre-registered protocol Additional file 3 ), hereafter referred to as ‘red flags’: those likely to inadvertently increase aggression (via resource guarding in group-housed male mice) [ 12 , 58 , 59 ], fear (caused by the frequent rotation of novel objects, or providing novel resources to old animals who may be neophobic) [ 60 , 61 ] or disinterest (possible in old animals, due to anhedonia) [ 21 ]. We also flagged any EH supplied for very short timeframes (i.e.…”

A mapping review of refinements to laboratory rat housing and husbandry

“…Similarly, rats were found to spend more time interacting with natural objects (rocks, sticks, dirt) as opposed to artificial objects (plastic toys) 41 , and spent more time interacting with objects in a cage containing multiple different objects of different types as opposed to multiple objects of the same type 42 . Yet, a preference for objects within the cage was not always observed, with one study finding that rats showed a preference for an empty compartment compared with a compartment containing six different objects (such as chains, ladders and blocks of wood) 43 .…”