Role of adult hippocampal neurogenesis in stress resilience

Abstract

There is a growing appreciation that adult hippocampal neurogenesis plays a role in emotional and cognitive processes related to psychiatric disorders. Although many studies have investigated the effects of stress on adult hippocampal neurogenesis, most have not focused on whether stress-induced changes in neurogenesis occur specifically in animals that are more resilient or more susceptible to the behavioural and neuroendocrine effects of stress. Thus, in the present review we explore whether there is a clear relationship between stress-induced changes in adult hippocampal neurogenesis, stress resilience and antidepressant-induced recovery from stress-induced changes in behaviour. Exposure to different stressors is known to reduce adult hippocampal neurogenesis, but some stressors have also been shown to exert opposite effects. Ablation of neurogenesis does not lead to a depressive phenotype, but it can enhance responsiveness to stress and affect stress susceptibility. Monoaminergic-targeted antidepressants, environmental enrichment and adrenalectomy are beneficial for reversing stress-induced changes in behaviour and have been shown to do so in a neurogenesis-dependant manner. In addition, stress and antidepressants can affect hippocampal neurogenesis, preferentially in the ventral hippocampus. Together, these data show that adult hippocampal neurogenesis may play a role in the neuroendocrine and behavioural responses to stress, although it is not yet fully clear under which circumstances neurogenesis promotes resilience or susceptibility to stress. It will be important that future studies carefully examine how adult hippocampal neurogenesis can contribute to stress resilience/susceptibility so that it may be appropriately exploited for the development of new and more effective treatments for stress-related psychiatric disorders.

Neural - hormonal responses to negative affective stimuli: Impact of dysphoric mood and sex

“…The critical role of hippocampus in providing negative feedback to the hypothalamus and thus in regulating HPA axis and stress response is well described (Dedovic et al, 2009; Hennerici & Szabo, 2014; Zschucke et al, 2015). Hippocampal dependent functions have been found to be impaired in numerous stress-related disorders (Lupien & McEwen, 1997; Herman et al, 2005, Goldstein et al, 2015) and developmental hippocampal abnormalities have been associated with risk for stress-related disorders (Seidman et al, 2002; Gilbertson et al, 2002; Meisenzahl et al, 2010; Anand & Dhikav, 2012; Levone et al, 2015; Pruessner et al, 2015). In fact, altered connectivity within this circuitry has been linked further to anxiety (Holmes et al, 2012), fear (Lebron-Milad et al, 2012) and reward (Admon et al, 2015).…”

Nerve Growth Factor(s) Mediated Hypothalamic Pituitary Axis Activation Model in Stress Induced Genesis of Psychiatric Disorders

“…In adult brain (also in humans) where neurogenesis keeps going on as a physiological event; as in hippocampal region (dentate gyrus) and subventricular zone (SVZ) of lateral ventricles (69,70); the role of NGFs in induced neurogenesis, remodelling of neuronal connections, and synaptic organizations with new experiences in these brain regions provide individual the ability to adapt to new life situations (71,72), a disruption of which may lead to aberrant behavioural changes alternatively described as psychiatric disorders (73).…”

The Avian Hippocampal Formation and the Stress Response

“…AHN in the temporal DG is more sensitive to chronic stress than AHN in the septal DG. Many more details of the role of the mammalian hippocampus in the stress response can be found in review articles by Jacobson and Sapolsky [1991], Radley [2012], and Levone et al [2015].…”