The influence of social environment on endocrine, cardiovascular and tissue responses in the rabbit

Abstract

Previous work from our lab demonstrated that social environment influences the progression of atherosclerosis in genetically hyperlipidemic rabbits. The purpose of the current study was to examine behavioral and physiological responses associated with these distinct chronic social conditions. Normolipidemic rabbits were exposed to one of 3 social environments for 4 hours/day over 20 weeks: 1) an Unstable Group in which animals were paired weekly with a different unfamiliar rabbit, 2) a Stable Group in which rabbits were paired with the same littermate for the entire study, and 3) an Individually Caged Group in which animals were socially isolated. It was found that the Unstable Group, characterized by increased agonistic behavior and relatively less affiliative behavior, exhibited physiological responses indicative of chronic stress (increased urinary norepinephrine, plasma cortisol, splenic weight, and decreased visceral fat and body weight compared to the other groups). These animals also had increased acute plasma oxytocin responses relative to the other groups 10 minutes into the social pairing. In contrast, the Stable Group exhibited more affiliative behavior and less stressful physiological and tissue responses. The Individually Caged Group had elevated urinary norepinephrine relative to the Stable Group, and they exhibited higher heart rates at the end of the study compared to the other groups, suggesting that this social environment is also associated with chronic sympathetic arousal. It was concluded that distinct social contexts lead to different patterns of behavioral and physiological responses, and these responses are relevant to the pathophysiology of atherosclerosis and cardiovascular disease.

Working Smarter Not Harder: Oxytocin Increases Domestic Dogs’ (Canis familiaris) Accuracy, but Not Attempts, on an Object Choice Task

“…We can speculate that this decrease in OT between sessions reflects the dogs being less stressed/aroused during session 3. Indeed, previous authors showed that OT release in brain and plasma could be related to acute stress events (Wotjak et al, 1998; Onaka et al, 2012; Noller et al, 2013). Despite the veterinarians’ attempts to reduce the stressfulness of the first blood sampling, it is possible that this handling could still trigger an increase in endogenous plasma OT levels to dampen the HPA axis activation, as already observed in mini-pigs (Marcet Rius et al, 2018) and beef heifers (Wagner et al, 2019).…”

Therapeutic Potential of Oxytocin in Atherosclerotic Cardiovascular Disease: Mechanisms and Signaling Pathways

“…It has been demonstrated that Watanabe Heritable Hyperlipidemic rabbits exposed to a consistent, stable social experience in association with higher blood OT levels exhibited more affiliative social behavior and less aortic atherosclerosis (Szeto et al, 2013). Social stress promoted the progression of atherosclerosis in these rabbits in association with increased urinary norepinephrine, plasma cortisol and splenic weight as well as less affiliative behavior and more stressful physiological and tissue responses (Noller et al, 2013). In human being, OT was positively associated with diminished stress among securely attached participants and had an attenuating effect on perceived stress due to adverse life events in old age (Emeny et al, 2015).…”

Laboratory Animal Behavior

“…While rabbits naturally live in large groups, they're not necessarily closely grouped: in a free-living population under study, the distance between individual does averages about 1 ft, and was up to 3 ft between a dominant and secondary buck (Lockley, 1961). A study of genetically hyperlipidemic rabbits, however, showed that rabbits housed either alone or in unstable social environments displayed physiologic parameters associated with chronic stress (Noller et al, 2013). A review of group-housed does for farm production revealed increased rates of injury and mortality as well as increased cortisol levels compared to individually housed does suggesting chronic stress (Szendro and McNitt, 2012).…”

“…A review of group-housed does for farm production revealed increased rates of injury and mortality as well as increased cortisol levels compared to individually housed does suggesting chronic stress (Szendro and McNitt, 2012). Groups of female rabbits can be formed, and the hierarchy established remains relatively stable if the group dynamic is held stable (Noller et al, 2013). While rabbits may be a 'social' species, clearly successfully socially housing them is not straightforward.…”