2009 Vol 99.pdf (2.45mb) - Primate Society of Great Britain

16
INVITED LECTURE
SOCIAL SUBORDINATION STRESS EFFECTS BEHAVIOR,
PATHOPHYSIOLOGY, AND DISEASE RISK IN ADULT
CYNOMOLGUS MACAQUES
Carol A. Shively, S.L. Willard, T.B. Clarkson, C.K. Henkel, D.P. Friedman,
T.C. Register
Wake Forest University School of Medicine, Winston-Salem, NC, USA
Presenter email: cshively@wfubmc.edu
While there are benefits to social group-living, there are also costs, one of
which is the stress that can result from the increased social density and
proximity inherent in a gregarious social organization. Social stress may
increase the risk of disease, and promote pathophysiological changes that
increase the risk of disease. We have studied disease susceptibility in adult
female cynomolgus monkeys (Macaca fascicularis) housed in small social
groups of 4 females each. Linear social status hierarchies form and are
stable over long time periods. In order to approximate as closely as possible
the human condition, the monkeys are fed a Western diet containing
moderate amounts of fat and cholesterol. Socially subordinate females
appear behaviourally and physiologically to be stressed relative to
dominants. They receive more aggression, are groomed less, spend more
time vigilant, less time being groomed, and more time alone than
dominants. Subordinates are hypercortisolemic, have higher heart rates in
response to a standardized stressor, suppressed reproductive function, and
decreased dopamine receptor 2 binding potential in the striatum. They are
more likely than dominants to deposit fat in the viscera, develop more
coronary artery atherosclerosis, and exhibit depressive behaviour.
Depressed monkeys are distinct from nondepressed subordinates
behaviourally and physiologically. For example, depressed monkeys, like
depressed human beings, have alterations in serotonin receptor 1a binding
throughout many areas of the brain which mediate emotional responses to
environmental events, and smaller anterior hippocampi. Thus, the stress of
social subordination in these small captive groups has extensive effects on
the behaviour, physiology and health of cynomolgus macaques.
Keywords: Stress, cortisol, serotonin, hippocampus, atherosclerosis,
visceral obesity, depression