Effect of a cage divider permitting social stimuli on stress and food intake in rats

Abstract

The need to obtain data from individual laboratory animals has forced many researchers to singlyhouse rodents and small animals. Isolation is an abnormal condition for many species, and adverse effects of single-housing on physiology and behavior threaten the validity of experimental results and generalization to humans, who are also social. This study assessed the practical use of a housing device -dubbed "Buddy Barrier" (BB) -that allows rats social stimulation in a paired-housing situation while at the same time permitting the collection of individual measures that traditionally require individual-housing. To assess stress responses to the BB, adult male rats were single or pairhousing for several days with and without a BB in the cage and fecal corticosterone metabolites (fCORT), food intake and body weight were monitored. Plasma corticosterone and adrenal catecholamine levels were also assessed at the end of the housing manipulation. Stress hormone measures did not differ in paired vs. singly-housed rats and paired rats quickly habituated to the BB taken in and out of the cage. Barring a trend for paired rats to eat more in the first 4hrs of the dark, there was no difference in 24hr intakes or body weight gain between singly and paired-housed rats. While the BB attenuated 24hr intakes in both groups, intakes normalized to non-BB conditions by the third BB reintroduction. A device such as the BB can enhance the welfare of animals by providing social enrichment without compromising the integrity of experimental manipulations in protocols that traditionally have required single-housing.

Moderate physical exercise attenuates the alterations of feeding behaviour induced by social stress in female rats

“…30,8,37 The measurement of metabolites of corticosterone in faeces, used in the present study, is a procedure previously validated in rats of both genders, demonstrating be a valuable tool to non-invasively monitor adrenocortical activity. 38,39 Given that blood collection to measure the serum corticosterone is an invasive technique that might compromise the welfare of the animal and may mask the effects of different condition assessment on endocrine functions. Under stressful conditions, such as the social isolation imposed to the animals of the present study, the HPA axis is overactivated by one evolutionary adaptation-disorders of circadian and ultradian rhythms, 40 and the negative feedback control of glicocorticoids on HPA axis becomes faulty.…”

Voluntary exercise in pregnant rats positively influences fetal growth without initiating a maternal physiological stress response

“…Measurement of fecal corticoids is well suited to the analysis of chronic stressors, as it provides a summated index of systemic corticoid production (9,44). We chose to assess fecal corticosterone over the first 4 h of the dark period, at the approximate nadir of its circadian cycle, as this is the time most likely to reflect a stress response (6,41). Reporting total fecal corticoids over time, rather than fecal corticoid concentration, provides a more accurate representation of systemic corticoid production by taking into account the amount of feces produced during the sampling time period (10).…”

Short-term voluntary exercise in the rat causes bone modeling without initiating a physiological stress response

“…Fecal corticosterone levels have been shown to reflect response to a stressor in rats, with fecal levels peaking 7-9 h after a plasma corticosterone peak (54). By collecting feces over the first 4 h of the dark period, we obtained samples at the approximate fecal corticosterone nadir, which is the time most likely to reveal a stress response (5,45,60). Although plasma corticosterone levels may be more indicative of acute stress, measurement of fecal corticoids is well-suited to analysis of longer-term stressors (hours to days), since it quantifies a summated index of systemic corticoids proven to reflect stress responses (8,48).…”

“…To measure the stress response to voluntary exercise, fecal samples were collected from all groups during three periods: preexercise, during early exercise (day 6 -9), and toward the end of the exercise period (day 18 -21). Feces were collected by a protocol similar to that described by Boggiano et al (5). Briefly, the cage bedding was changed 1 h before the start of the dark period.…”

“…Urine-soaked feces were discarded (this occurred only one time, since the high-quality bedding instantly absorbed any voided urine). The first 4 h of the dark period are approximately the time of the fecal corticosterone nadir (5,9), at which time between-group differences in corticosterone would be most apparent (60). Female rats produce varying levels of fecal corticoids during the different phases of their estrous cycle (9).…”