Functional magnetic resonance imaging study on anxiety and depression disorders induced by chronic restraint stress in rats

Persistent and negative stress stimulation is one of the most important factors leading to anxiety and depression in individuals, and it can negatively affect the normal function and structure of brain-related regions. However, the maladaptive changes of brain neural networks in anxiety and depression induced by chronic stress have not been explored in detail. In this study, we analyzed the changes in global information transfer efficiency, stress related blood oxygen level dependent (BOLD)- and diffusion tensor imaging (DTI)- signals and functional connectivity (FC) in rat models based on resting-state functional magnetic resonance imaging (rs-fMRI). The results showed that compared to control group, rats treated with chronic restraint stress (CRS) for 5 weeks had reconstructed the small-world network properties. In addition, CRS group had increased coherence and activity in bilateral Striatum (ST_R & L), but decreased coherence and activity in unilateral (left) Frontal Association Cortex (FrA_L) and unilateral (left) Medial Entorhinal Cortex (MEC_L). DTI analysis and correlation analysis confirmed the disrupted integrity of MEC_L and ST_R & L and their correlation to anxiety- and depressive-liked behaviors. Functional connectivity further showed these regions of interest (ROI) had decreased positive correlations with several brain areas, respectively. Our study comprehensively revealed the adaptive changes of brain neural networks induced by chronic stress and emphasized the abnormal activity and functional connectivity of ST_R & L and MEC_L in the pathological condition.

[Features of endocrine function of the pancreas with aging in nonhuman primates with various types of adaptive behavior.]

An increasing number of studies are devoted to the study of the relationship of mental disorders, such as depression and anxiety, with the risk of developing type 2 diabetes mellitus. However, in the literature there are practically no publications on the study of the relationship of the features of higher nervous activity, in particular, adaptive behavior, in healthy individuals with the risk of developing age-related dysfunction of the pancreatic islet apparatus (PIA). The purpose of this study was to investigate features of the functioning of the PIA during aging in individuals with normal standard behavior (SB), as well as anxiety- and depressive-like behavior (DAB) in experiments on nonhuman primates. 76 physically healthy young mature and old female rhesus monkeys with SB and DAB were used in the experiments. Old animals were divided into subgroups with normal (NW) and excess (EW) body weight. All young animals were characterized by NW. The function of PIA was assessed using a glucose tolerance test. Intergroup differences in the functioning of the PIA in young animals were revealed, which were characterized by signs of impaired early insulin response, apparently due to a decrease in the sensitivity of β-cells of the pancreas to glucose. With aging, the function of the PIA was damaged in all animals, but the features of its changes depended on both the affiliation to a particular behavioral group and the animal's body weight. During aging in animals with SB, the development of relative insulin resistance of peripheral tissues was observed, accompanied by impaired glucose tolerance and a compensatory increase in the secretory activity of the PIA, which were more pronounced in animals with EW. Age-related dysfunction of the PIA in animals with DAB and NW was similar with age-related changes in the PIA function in animals with SB and NW. At the same time, with aging, animals with DAB and EW showed a more significant peak concentration of glucose than that of old animals with SB and EW, accompanied by a minimum «disappearance» rate of glucose from the circulation and significantly lower insulin secretion than this in animals with SB and EW. Thus, age-related dysfunctions of the PIA in primates with SB and DAB are unidirectional with the development of insulin resistance, impaired glucose tolerance and a compensatory increase in insulin secretion, which, however, in old animals with DAB and EW are accompanied by exhaustion of the PIA function, increasing the risk of developing type 2 diabetes mellitus.