Research Grants 2006-2007

The impact of housing conditions on the stress response of rats in the laboratory setting

Margaret A. Rose
Professor, Faculty of Medicine, UNSW Area Director, Research Management, Prince of Wales Hospital, Randwick NSW

Objective: This study will provide new information relevant to the validation of the role of environmental conditions in achieving the goals of Refinement and Reduction. Thus, through simple changes to routine animal husbandry practices, a significant reduction in the level of distress animals may experience under laboratory conditions could be achieved.

Specific Aim: To test whether the physical complexity of the environmental conditions which a rat experiences from weaning affect its ability to cope with potentially stressful experimental procedures.

Background: Providing laboratory animals with conditions which meet their species-specific needs is essential for their wellbeing and various strategies, often described under the general heading of environmental enrichment (EE), have been proposed to achieve this. However, there are important differences in the conditions described as EE in the neurosciences and the ways in which EE is provided for laboratory animals. In the former EE encompasses a complex of environmental experiences designed to enhance the animal's cognitive and emotional development, whereas, the latter most often involves simple modifications to physical structures. However, data from the neurosciences show that the design and complexity of housing conditions influence the behavioural and neurological development of rats with significant effects on cognitive and emotional development.

The evidence that EE affects a rat's capacity to cope with novelty by modulating anxiety and distress, suggests that the construction of the environment has significant implications, not only in achieving comfortable living conditions for laboratory animals but also, in promoting Refinement. To date little attention has been paid to the critical application of these studies to the day to day management of laboratory animal colonies. However, to evaluate the potential benefits of environmental conditions on animal welfare and in achieving Refinement, data relating to emotionality and physiological response to stressors would be informative. These are both areas where there is limited data and the influence of physical environmental enrichment is unclear. The proposed study will focus on both behavioural and neurofunctional measures of emotionality and physiological measures of acute and chronic stress. The influences of physical environmental conditions of varying complexity and responses to psychological and physical stressors will be tested.

Experimental Design: Inbred Wistar rats will be housed in one of three environmental conditions from weaning until the end of the study:

Group 1 — conventional tub with bedding
Group 2 — conventional tub with bedding, nesting material, a PVC shelter and wood chips
Group 3 — as for Group 2 with PVC tunnels, wooden blocks, and objects (variety of sizes, shapes and colours) which will be changed weekly.

At weaning (D21), pups will be segregated into male and female groups, 4 siblings in each, and will remain in these cohorts for the remainder of the study. On D49, boxes in each environmental condition will be randomly allocated to one of three treatments for the next 7 days —

control
single housing
daily restraint with subcutaneous saline injection

On D57, boxes will be designated either for (1) behavioural tests of emotionality — the open-field test and the elevated maze test will be performed with a 7 day interval between testing - or (2) a functional-anatomical study, involving evoked neuronal activation of brain regions known to mediate emotional behaviours. On D67 (3 days after the second behaviour test), these animals will either undergo an acute restraint test which will measure corticosterone response, or be killed and atria dissected for an in vitro study of beta-adrenoceptor responsiveness.

Relevance to goals of 3R's: Data are relevant to the goals of Refinement and Reduction. Enabling an animal to modulate its response to stressors will promote its wellbeing and reduce the potential of that stress response as a confounding variable in data collection.

Future studies will look at the role of handling, the complimentary influences of handling and EE, the potential benefits of early life experiences and strain differences.