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Postnatal handling alters the activation of stress-related neuronal circuitries
1Laboratory of Molecular Neuroendocrinology, Institute of Experimental Medicine, Budapest, Szigony u. 43, 1083, Hungary. abraham@koki.hu
Insights
Early life handling, a form of environmental enrichment, reduces stress responses in adult rats. This early experience attenuates the reactivity of stress-related neural circuits, demonstrating long-term benefits.
Area of Science:
- Neuroscience
- Developmental Biology
- Stress Physiology
Background:
- Early life experiences significantly shape stress axis development.
- Postnatal handling is a key environmental factor influencing neurodevelopment.
- Understanding these effects is crucial for stress-related disorders.
Purpose of the Study:
- To investigate the long-term impact of postnatal handling on stress circuitry reactivity.
- To compare neuronal activation patterns in handled versus non-handled adult rats under stress.
- To determine stressor specificity in neuronal responses based on early life experience.
Main Methods:
- Adult rats, handled during the first 21 days of life, were exposed to physical (ether) or emotional (restraint) stress.
- Neuronal activation was assessed by measuring the induction and distribution of the immediate-early gene c-Fos.
- Spatial and temporal patterns of c-Fos expression were analyzed in various brain regions.
Main Results:
- Both ether and restraint stress activated key stress-related brain areas, including the hypothalamic paraventricular nucleus.
- Handled rats showed reduced c-Fos expression in several brain regions (PVN, BNST, CeA, hippocampus, piriform cortex, Cg) compared to controls.
- The timing and intensity of c-Fos induction varied depending on the stressor and early life handling.
- Stressor-specific activation patterns were observed across multiple brain regions.
Conclusions:
- Early postnatal handling attenuates the reactivity of stress-related neuronal circuits in adult rats.
- Environmental enrichment during development has lasting effects on the brain's stress response system.
- These findings provide functional anatomical evidence for the neurobiological impact of early life experiences on stress resilience.
Abstract:
Postnatal handling, as a crucial early life experience, plays an essential role in the development of hypothalamo-pituitary-adrenal axis responses to stress. The impact of postnatal handling on the reactivity of stress-related neuronal circuitries was investigated in animals that were handled for the first 21 days of life and as adults they were exposed to physical (ether) or emotional (restraint) challenge. To assess neuronal activation we relied on the induction of immediate-early gene product c-Fos and analysed its spatial and temporal distribution at various time intervals after stress. Ether and restraint commonly activated parvocellular neurons in the hypothalamic paraventricular nucleus, and resulted in activation of brain areas providing stress-related information to the hypothalamic effector neurons and/or in regions governing autonomic and behavioural responses to stress. Beyond these areas, the strength and timing of c-Fos induction showed stressor specificity in olfactory and septal region, basal ganglia, hypothalamus, hippocampal formation, amygdala and brainstem. Handled rats displayed a lower number of c-Fos-positive cell nuclei and weaker staining intensity than non-handled controls in the hypothalamic paraventricular nucleus, bed nucleus of stria terminalis, central nucleus of amygdala, hippocampus, piriform cortex and posterior division of the cingulum. Significant differences were revealed in timing of c-Fos induction as a function of stressor and early life experience. Together, these data provide functional anatomical evidence that environmental enrichment in the early postnatal period attenuates the reactivity of stress-related neuronal circuitries in the adult rat brain.