Social Stress Increases Male Neurogenesis

Adult neurogenesis, the creation and integration of new brain neurons, was thought impossible until about 20 years or so ago, but now we know that aerobic exercise, father-child bonding in the early weeks of life, learning, and the SSRI antidepressants can all generate neurogenesis, largely in the hippocampus.

Exciting new research in adult monkeys suggests that social stress also can create neurogenesis. The Proceedings of the National Academy of Sciences has published this open access article on the research.

Stress coping stimulates hippocampal neurogenesis in adult monkeys

1. David M. Lyons^a,¹,
2. Paul S. Buckmaster^b,
3. Alex G. Lee^a,
4. Christine Wu^b,
5. Rupshi Mitra^a,
6. Lauren M. Duffey^a,
7. Christine L. Buckmaster^a,
8. Song Her^a,²,
9. Paresh D. Patel^c, and
10. Alan F. Schatzberg^a

+ Author Affiliations

1. Departments of ^aPsychiatry and Behavioral Sciences and
2. ^bComparative Medicine, Stanford University Medical Center, Stanford, CA 94305; and
3. ^cDepartment of Psychiatry, Molecular and Behavioral Neuroscience Institute, University of Michigan Medical Center, Ann Arbor, MI 48109

• ↵²Present address: Korea Basic Science Institute, 192-1 Hyoja2-Dong, Chuncheon, Gangwon-Do 200-701, Korea.

1. Edited by Fred Gage, The Salk Institute, San Diego, CA, and approved July 6, 2010 (received for review December 16, 2009)

Abstract

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 exposed to 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 previously confirmed that cortisol levels initially increase and then are restored to prestress 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 exposure to intermittent social 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 hippocampal neural circuits. These findings support recent indications that stress coping stimulates hippocampal neurogenesis in adult rodents. Psychotherapies designed to promote stress coping potentially have similar effects in humans with major depression.

In human studies, we know that prolonged or frequent stress, at least in children, shrinks the hippocampus and decreases its ability to generate new neurons. So this research changes the basic assumptions a bit, assuming however that the organism is able to handle the stress in an adaptive way.

These findings may also be useful in resiliency studies.

Here is a little more from the article that explains more about the research and its implications.

Although stress generally inhibits proliferation of new cells (1, 2) and thereby decreases neurogenesis in the hippocampus (3–5), recent studies of rodents suggest that coping with mild intermittent stress increases adult neurogenesis in the hippocampal dentate gyrus (6). Psychotherapies designed to promote coping in humans with depressive disorders may potentially have similar effects (7, 8), but the neurogenic potential of stress coping has not been examined in human or nonhuman primates. Studies of primates are important for understanding neurogenesis in adult brain systems with established neural circuits and life spans that differ significantly from rodents (9).

For most adult human and nonhuman primates, coping with stressful psychosocial demands spontaneously occurs in the absence of therapeutic interventions or guidance (10, 11). Male squirrel monkeys, for example, travel alone, in pairs, or in all-male groups that undergo stressful changes in membership. Changing male social associations occur in free ranging naturalistic conditions because of competition for limited access to residency in mixed-sex groups (12, 13). As evidence of coping, we and other investigators determined that plasma levels of cortisol initially increase and then are restored to prestress levels during intermittent social separations and new pair formations (14–16). Follow-up studies with exogenous cortisol further established that feedback regulation of the hypothalamic-pituitary-adrenal (HPA) axis is not impaired (17). Moreover, we found that plasma levels of adrenocorticotropic hormone (ACTH) measured in undisturbed home cage conditions and after exposure to a nonsocial stressor (i.e., restraint) do not differ significantly in males exposed to prior intermittent separations and new pair formations compared with control monkeys housed continuously with a familiar male (17).

Good stuff.

Tags: gene expression, learning, neuroplasticity, resilience, hippocampus, PNAS, neurogenesis, adult monkeys, psychology, brain, research, neuroscience, social stress, cortisol, males, competition, intermittent stress, hypothalamic-pituitary-adrenal axis, HPA axis, resiliency