[Early experience, stressful dysregulation of the hormonal axis and age-related vulnerability to neurodegenerative processus: a longitudinal study in the rat].

The deleterious effects of particular environmental situations have been suspected to augment the repercussions of cerebral injuries leading to increased vulnerability during ageing. The relationship between the hormones of the hypothalamo-pituitary-adrenal axis, mainly glucocorticosteroids, and cerebral structures like the hippocampus has been the subject of intense investigation in the recent years. Data suggest that long-term elevated blood levels of these hormones can induce neuronal alterations leading to cognitive dysfunction. This hypothesis has been tested with relevant animal models of normal/abnormal ageing. The models are based on the existence of considerable inter-individual differences in the degree of age-related cognitive impairments observed in rodents. Results show that long-term glucocorticosteroid exposure induces cerebral changes related to the action of these hormones on their central receptors. Experimental data are in accordance with clinical investigations suggesting that hormonal changes, and chronic life events, could be considered as a predictive factor of future cognitive dysfunction.