2 Neuroscience2.10 Neurodevelopment and neuroplasticity

2.10.4.1 Neurobiological effects of stress pre-, peri and postnatally, developmentally and in adults

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Written by Resident Doctor Committee · Published

Prenatal and perinatal stress

  • Placental 11-beta hydroxysteroid dehydrogenase type 2 converts maternal cortisol to inactive cortisone, forming a partial barrier that protects the foetus.

  • Foetal programming is lasting change in hypothalamic-pituitary-adrenal (HPA), autonomic, immune or metabolic development after intrauterine exposures.

  • Hypoxia causes glutamate-mediated excitotoxicity, which damages periventricular white matter in preterm infants and the basal ganglia and thalamus at term.

Childhood maltreatment

  • Early maltreatment disturbs development of the fronto-limbic network: the amygdala becomes hyper-reactive while prefrontal regulation weakens, and pruning is altered.

  • Reduced hippocampal volume is the most replicated structural finding after childhood trauma, because the hippocampus is highly sensitive to glucocorticoids. The hypothalamus changes in function but does not shrink consistently.

  • Chronic maltreatment can flatten the diurnal cortisol rhythm.

  • Weaver (2004) showed that low maternal licking and grooming in rats increased hippocampal glucocorticoid receptor promoter methylation and stress reactivity, and that cross-fostering reversed both effects.

Follow the red glucocorticoid arrows back from the adrenal cortex to the GR and MR receptors in the hippocampus, which shows why the hippocampus is so sensitive to glucocorticoids and why it is the structure that shrinks most reliably after childhood trauma. Raabe FJ and Spengler D, CC BY 3.0, via Wikimedia Commons

Stress in adults

Wave

Timing

Effects

Sympathoadrenal and noradrenergic

Within seconds

Cardiac output and vigilance rise

Glucocorticoid

Peaks at 20 to 30 minutes

Glucose is mobilised and the immune response restrained

  • Noradrenaline and glucocorticoids strengthen emotional memory consolidation through the basolateral amygdala but impair retrieval.

  • Allostatic load (McEwen and Stellar) is the cumulative multisystem cost of repeated or prolonged stress responses, not a cortisol measurement.

  • In animals, chronic stress causes hippocampal CA3 dendritic retraction, reduced dentate neurogenesis and basolateral amygdala hypertrophy.

Revision material for the MRCPsych examinations. Not clinical guidance, and not for use in patient care.