Moncek et al. (2004) compared the stress response of male Wistar rats kept under varioius conditions to gentle 1-minute handling sessions. of male Wistar ratsOne set of rats was kept in groups of three or four animals in barren cages, with while the other subjects were taken from groups of ten animals living in five times larger cages that were five times larger and that wereenriched with various toys, tunnels, swings and running wheels. The large-group/, enriched rats from large groups showed a significantly lower ACTH, corticosterone and adrenaline response to handling than the small-group/, nounenriched rats from small groups. It is not clear whether the stress buffering effect was exerted bydue to the larger number of group members, the larger space available to each subject, the enrichment, or , (as is presumably the case) a combination of these factors.

Belz et al. (2003) studied jugular vein-cannulated, individually housed female Sprague-Dawley rats who lived in 1100 cm² large cages that were either barren or enriched with rubber toys for gnawing and squares of compressed cotton fiber for shredding. TheWhile living space was the same for all animals, but those of in enriched cages were not only were easier to handle but they also showed a significantly lower endocrine [adrenocorticotropin] stress response to intraperitoneal injection. This effect could not be verified in male rats. Sharp et al. (2005) assessed cardiovascular stress responses to common handling procedures in SH rats bearing radiotelemetry transmitters, who were individually housed in 930 cm² large cages that were either barren or enriched with a simulated burrow, a feeding enrichment gadget Note to author: if another adjective is necessary, find a different one. Double use of 'enrichment' in this sentence is confusing., and a shredding-and-nesting item. While blood pressure was not affected by enrichment, heart rate responses to subcutaneous injection and to tail vein injection were significantly lower in enriched versus non-unenriched rats, indicating that enrichment had a stress buffering effect during these common procedures. This effect could not be replicated in Sprague-Dawley rats.