Chronic social stress reduces dendritic arbors in CA3 of hippocampus and decreases binding to serotonin transporter sites

Abstract

Male rats housed in mixed-sex groups in a visible burrow system (VBS) form a dominance hierarchy in which subordinate animals show stress-related changes in behavior, endocrine function and neurochemistry. Dominants also appear to be moderately stressed compared to controls, although these animals do not develop the more pronounced behavioral and physiological deficits seen in the subordinates. In the present study, we examined the effects of chronic psychosocial stress on the morphology of Golgi-impregnated CA3 pyramidal neurons. In addition, since serotonin has been implicated in the mechanisms mediating the dendritic remodeling seen with other chronic stress regimens, we used quantitative autoradiography to measure binding to the serotonin transporter (5HTT) in hippocampus and dorsal and median raphe. Chronic social stress led to a decrease in the number of branch points and total dendritic length in the apical dendritic trees of CA3 pyramidal neurons in dominant animals compared to unstressed controls; subordinates also had a decreased number of dendritic branch points. [(3)H]paroxetine binding to the 5HTT was decreased in Ammon's horn in both dominants and subordinates compared to controls, while 5HTT binding remained unchanged in dentate gyrus and raphe. The similarity of the changes in 5HTT binding and dendritic arborization between both groups of VBS animals, despite apparent differences in stressor severity, suggests that these changes may be part of the normal adaptive response to chronic social stress. The mechanisms underlying dendritic remodeling in CA3 pyramidal neurons are likely to involve stress-induced changes in glucocorticoids and in 5HT and other transmitters.

Social stress and recovery: implications for body weight and body composition

“…We have confirmed previous reports that social stress results in significant BW loss in both DOM and SUB rats housed in a VBS (5,8,11,21,34,56). We further found that fat distribution changes differentially in SUB and DOM rats.…”

Life-Long Hippocampal Neurogenesis: Environmental, Pharmacological and Neurochemical Modulations

“…In congruence with these various sets of data, a decrease in neurogenesis was reported in subordinate tree shrews that had been subjected to repeated social interaction stress (i.e. by daily introduction of a naive animal into the cage of a socially experienced one, which leads to clear-cut dominant/subordinate relationships) [57][58][59]. Similarly, repeated intermittent social defeat for 10 successive days was found to cause a significant reduction in hippocampal cell proliferation in mice [60].…”

cDNA Microarray Analysis of Gene Expression in the Cerebral Cortex and Hippocampus of BALB/c Mice Subjected to Chronic Mild Stress

“…A reduced hippocampal volume was observed in the depressed patients (Sheline et al 2003) and in a depression animal model (Fuchs et al 2004;Jayatissa et al 2006). Prolonged psychosocial stress in monkeys is associated with loss of hippocampal neurons (Uno et al 1989), whereas repeated psychosocial stress in a primitive primate, the tree shrew, and in rats causes hippocampal CA3 pyramidal neurons to undergo dendritic atrophy McKittrick et al 2000). A similar structural change is observed in rats subjected to a chronic repeated restraint stress paradigm.…”