Two Adverse Early Life Events Induce Differential Changes in Brain CRH and Serotonin Systems in Rats along with Hyperphagia and Depression

Abstract

Background: Different types of stress inflicted in early stages of life elevate the risk, among adult animals and humans, to develop disturbed emotional-associated behaviors, such as hyperphagia or depression. Early-life stressed (ELS) adults present hyperactivity of the hypothalamus-pituitary-adrenal (HPA) axis, which is a risk factor associated with mood disorders. However, the prevalence of hyperphagia (17%) and depression (50%) is variable among adults that experienced ELS, suggesting that the nature, intensity, and chronicity of the stress determines the specific behavioral alteration that those individuals develop. Methods: We analyzed corticosterone serum levels, Crh, GR, Crhr1 genes expression in the hypothalamic paraventricular nucleus, amygdala, and hippocampus due to their regulatory role on HPA axis in adult rats that experienced maternal separation (MS) or limited nesting material (LNM) stress; as well as the serotonergic system activity in the same regions given its association with the corticotropin-releasing hormone (CRH) pathway functioning and with the hyperphagia and depression development. Results: Alterations in dams’ maternal care provoked an unresponsive or hyper-responsive HPA axis function to an acute stress in MS and LNM adults, respectively. The differential changes in amygdala and hippocampal CRH system seemed compensating alterations to the hypothalamic desensitized glucocorticoids receptor (GR) in MS or hypersensitive in LNM. However, both adult animals developed hyperphagia and depression-like behavior when subjected to the forced-swimming test, which helps to understand that both hypo and hypercortisolemic patients present those disorders. Conclusion: Different ELS types induce neuroendocrine, brain CRH and 5-hydroxytriptamine (5-HT) systems’ alterations that may interact converging to develop similar maladaptive behaviors.