Interaction Effect of Social Isolation and High Dose Corticosteroid on Neurogenesis and Emotional Behavior

Abstract

Hypercortisolemia is one of the clinical features found in depressed patients. This clinical feature has been mimicked in animal studies via application of exogenous corticosterone (CORT). Previous studies suggested that CORT can induce behavioral disturbance in anxious-depressive like behavior, which is associated with suppressed neurogenesis. Hippocampal neurogenesis plays an important role in adult cognitive and behavioral regulation. Its suppression may thus lead to neuropsychiatric disorders. Similar to the effects of CORT on the animals’ depression-like behaviors and neurogenesis, social deprivation has been regarded as one factor that predicts poor prognosis in depression. Furthermore, social isolation is regarded as a stressor to social animals including experimental rodents. Hence, this study aims to examine if social isolation would induce further emotional or anxiety-like behavior disturbance and suppress neurogenesis in an experimental model that was repeatedly treated with CORT. Sprague-Dawley rats were used in this study to determine the effects of different housing conditions, either social isolated or group housing, in vehicle-treated control and CORT-treated animals. Forced swimming test (FST), open field test (OFT) and social interaction test (SIT) were used to assess depression-like, anxiety-like and social behaviors respectively. Immunohistochemistry was performed to quantify the number of proliferative cells and immature neurons in the hippocampus, while dendritic maturation of immature neurons was analyzed by Sholl analysis. Social isolation reduced latency to immobility in FST. Furthermore, social isolation could significantly reduce the ratio of doublecortin and bromodeoxyuridine (BrdU) positive cells of the neurogenesis assay under CORT-treated condition. The current findings suggested that the behavioral and neurological effect of social isolation is dependent on the condition of hypercortisolemia. Furthermore, social isolation may possibly augment the signs and symptoms of depressed patients with potential alteration in neurogenesis.

Protective Effects of Melatonin on Neurogenesis Impairment in Neurological Disorders and Its Relevant Molecular Mechanisms

“…According to the neurogenesis hypothesis of depression, the disturbance of mood and emotion is linked to the impairment of neurogenesis, and restoration of neurogenesis would be a critical factor for the remission from the disease [ 2 , 46 , 47 , 48 ]. If neurogenesis is suppressed, the beneficial effects of antidepressants would be abolished, which may indicate that reversing neurogenesis deficits is a potential therapeutic target of depression [ 49 ].…”

Behavioral and neurological improvement by Cydonia oblonga fruit extract in chronic immobilization stress rats

“…Chronic stress has long been associated with the development of depression, one of the major psychiatric disorders worldwide. Depressed patients are usually accompanied by dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis (Chan et al, 2017), mood disturbance, sleep abnormalities (Nollet et al, 2012), anhedonia, and anxiety (Micheli, Ceccarelli, D'Andrea, & Tirone, 2018). Moreover, clinical studies showed a reduction of hippocampal volume, and the atrophy of the hippocampus and prefrontal cortex in patients with depression (Banasr, Dwyer, & Duman, 2011; Micheli et al, 2018; Toda, Parylak, Linker, & Gage, 2019).…”

The effect of voluntary wheel running on the antioxidant status is dependent on sociability conditions

“…The same effect was not observed in non-predisposed Wistar rats, suggesting that predisposition to the effects of stress is a determining factor for behavior despair following SIS ( Zanier-Gomes et al, 2015 ). Moreover, several reports also revealed that SIS significantly increased the immobility time of NMRI and C57BL/6J mice or Sprague-Dawley rats submitted to the FST ( Chan et al, 2017 ; Cho et al, 2017 ; Dávila-Hernández et al, 2018 ; Haj-Mirzaian et al, 2015 , Haj-Mirzaian et al, 2019 ). The discrepancies of our results in the behavior despair test, compared to the literature data, could be due to several factors, including biological factors such as strain, age, body weight, gender, and individual differences between animals.…”