Stress coping stimulates hippocampal neurogenesis in adult monkeys.

D.M. Lyons; P.S. Buckmaster; A. Lee; C. Wu; R. Mitra; L.M. Duffey; C.L. Buckmaster; S. Her; P.D. Patel; A.F. Schatzberg
Society for Neuroscience. 2010.


Coping with intermittent social stress is an essential aspect of living in complex social environments. Coping tends to counteract the deleterious effects of stress and is thought to induce neuroadaptations in corticolimbic brain systems. Here we test this hypothesis in adult squirrel monkey males housed in conditions enriched with intermittent social separations and new pair formations. These manipulations simulate conditions that typically occur in male social associations because of competition for limited access to residency in mixed-sex groups. As evidence of coping, we initially confirmed that cortisol levels increase and then return to pre-stress levels within several days of each separation and new pair formation. Follow-up studies with exogenous cortisol further established that feedback regulation of the hypothalamic-pituitary-adrenal axis is not impaired. Now we report that living in conditions enriched with intermittent separations and new pair formations increased hippocampal neurogenesis in squirrel monkey males. Hippocampal neurogenesis in rodents contributes to spatial learning performance and in monkeys we found that spatial learning was enhanced in conditions that increased hippocampal neurogenesis. Corresponding changes were discerned in the expression of genes involved in survival and integration of adult-born granule cells into functional neural circuits. These findings support the suggestion that environmental enrichment effects widely reported in rodents may reflect, in part, the process of coping with novelty and complexity. Psychotherapies designed to promote stress coping may potentially have similar hippocampal neurogenic effects in humans with major depression.