The effect of depressive-like behavior and antidepressant therapy on social behavior and hierarchy in rats

Comparative Evaluation of Antidepressant and Anxiolytic Effects of Escitalopram, Crocin, and their Combination in Rats

Background

Chronic stress can lead to anxiety and depression. Escitalopram is a selective serotonin reuptake inhibitor (SSRI), and crocin is a natural compound derived from saffron. Both of them are used to treat these disorders in clinical and traditional medicine, respectively. This study compared the antidepressant and anxiolytic effects of escitalopram, crocin, and their combination in rats.

Materials and Methods

Rats were divided into nine groups: control, sham, rest-depression, depression-rest, depression-crocin, depression-escitalopram10, depression-escitalopram20, depression-escitalopram10-crocin, and depression-escitalopram20-crocin. Forced swimming and open field tests (FST and OFT, respectively) were used to evaluate depression, anxiety, and locomotor activity.

Results

In the FST, the immobility time on day 28 significantly decreased in all depressed groups that received escitalopram, crocin, and their combination compared to the rest-depression group. Whereas, conversely, the time spent at the center in the OFT was significantly higher in similar comparisons. The total distance traveled by the OFT was significantly lower in all depressed groups, except for the depression-escitalopram10 and depression-escitalopram20 groups. The total distance traveled was significantly higher in the depression-escitalopram20 compared to the rest-depression group.

Conclusion

Crocin, both doses of escitalopram and their combination, reduced depression. A high dose of escitalopram, with and without crocin, was partially more effective than a low dose of escitalopram in reversing depression. There was anxiety-like behavior observed after inducing depression with and without a recovery period. Whereas, crocin alone and both doses of escitalopram, with and without crocin, decreased anxiety-like behaviors in subjects with depression. This effect may be attributed to a modulation of brain neurotransmitter ratios.

Inhibition of ferroptosis alleviates chronic unpredictable mild stress-induced depression in mice via tsRNA-3029b

Depression is a common mental illness. Ferroptosis is a form of cell death that may be responsible for neurological disease, but the role of ferroptosis in depression remains unclear. tRNA-derived small RNA (tsRNA) is an emerging non-coding small RNA, making it an important medium for studying neurological diseases. Chronic unpredictable mild stress (CUMS) was used to construct the depression model in mice, which was treated with ferrostatin-1 (Fer-1). Classical behavioral test, immunofluorescence and small RNA sequencing were used to detect depression-like behaviors, neuronal proliferation and the expression profile of tsRNAs in mice, respectively. The primary neuronal cell damage model was constructed by corticosterone (CORT), and the function of key tsRNA was investigated by quantitative real-time PCR, western blot and CCK-8 assays. Here, Fer-1 reduced the depression-like behavior of CUMS-induced mice and promoted neuronal growth. In addition, CUMS caused the disorder of tsRNA expression profile in hippocampal tissues of mice, and Fer-1 alleviated the abnormal tsRNA expression, among which tsRNA-3029b was an effective target. In vitro experiments manifested that ROS accumulation and decreased expression of SLC7A11 and GPX4 were found in CORT-induced depression-like cell model, suggesting that ferroptosis was involved in neuronal injury. However, inhibition of tsRNA-3029b suppressed neuronal cell ferroptosis and facilitated neuronal regeneration. In conclusion, Fer-1 showed an antidepressant effect in CUMS-induced mice and alleviated the abnormal expression profile of tsRNA. tsRNA-3029b was a key target in depression, and silencing of tsRNA-3029b reduced the occurrence of ferroptosis and protected neurons from injury, which may provide novel target for the treatment of depression.

Blood glutamate scavenging as a novel glutamate-based therapeutic approach for post-traumatic brain injury anxiety and social impairment

Traumatic brain injury (TBI) is a serious condition that is associated with an increased risk of severe, long-term psychiatric consequences. Drugs that target the glutamatergic system have proven successful in treating both TBI and many of its psychiatric sequelae. Blood glutamate scavengers (BGS) cause a decrease in blood glutamate levels, leading to a reduction in glutamate's concentration gradient from the brain to the blood and decreased levels of brain glutamate. This study evaluated the BGS pyruvate as a treatment for TBI-related neuropsychiatric conditions in a rat model. 213 rats were divided into four groups in a 2 × 2 design: Sham or TBI rats treated with pyruvate or control treatment. Magnetic resonance imaging, neurological status, brain glutamate and blood glutamate levels were assessed following the injury. Four weeks after the start of treatment, all rats underwent behavioral tests to assess anxious behavior and social impairment (aggressive and hierarchical behavior). Rats responded positively to pyruvate in several tasks, lowering brain glutamate levels and reducing anxiety and depression, as well as modulating TBI-related changes in social behavior. Glutamate scavenging with pyruvate may be an effective therapeutic option for post-TBI behavioral changes by reducing associated elevations in brain glutamate levels.

Introducing a depression-like syndrome for translational neuropsychiatry: a plea for taxonomical validity and improved comparability between humans and mice

Depressive disorders are the most burdensome psychiatric disorders worldwide. Although huge efforts have been made to advance treatment, outcomes remain unsatisfactory. Many factors contribute to this gridlock including suboptimal animal models. Especially limited study comparability and replicability due to imprecise terminology concerning depressive-like states are major problems. To overcome these issues, new approaches are needed. Here, we introduce a taxonomical concept for modelling depression in laboratory mice, which we call depression-like syndrome (DLS). It hinges on growing evidence suggesting that mice possess advanced socioemotional abilities and can display non-random symptom patterns indicative of an evolutionary conserved disorder-like phenotype. The DLS approach uses a combined heuristic method based on clinical depression criteria and the Research Domain Criteria to provide a biobehavioural reference syndrome for preclinical rodent models of depression. The DLS criteria are based on available, species-specific evidence and are as follows: (I) minimum duration of phenotype, (II) significant sociofunctional impairment, (III) core biological features, (IV) necessary depressive-like symptoms. To assess DLS presence and severity, we have designed an algorithm to ensure statistical and biological relevance of findings. The algorithm uses a minimum combined threshold for statistical significance and effect size (p value ≤ 0.05 plus moderate effect size) for each DLS criterion. Taken together, the DLS is a novel, biologically founded, and species-specific minimum threshold approach. Its long-term objective is to gradually develop into an inter-model validation standard and microframework to improve phenotyping methodology in translational research.

Traumatic brain injury-induced submissive behavior in rats: link to depression and anxiety

Traumatic brain injury (TBI) affects millions of people worldwide, many of whom are affected with post-TBI mood disorders or behavioral changes, including aggression or social withdrawal. Diminished functionality can persist for decades after TBI and delay rehabilitation and resumption of employment. It has been established that there is a relationship between these mental disorders and brain injury. However, the etiology and causal relationships behind these conditions are poorly understood. Rodent models provide a helpful tool for researching mood disorders and social impairment due to their natural tendencies to form social hierarchies. Here, we present a rat model of mental complications after TBI using a suite of behavioral tests to examine the causal relationships between changes in social behavior, including aggressive, hierarchical, depressive, and anxious behavior. For this purpose, we used multivariate analysis to identify causal relationships between the above post-TBI psychiatric sequelae. We performed statistical analysis using principal component analysis, discriminant analysis, and correlation analysis, and built a model to predict dominant-submissive behavior based on the behavioral tests. This model displayed a predictive accuracy of 93.3% for determining dominant-submissive behavior in experimental groups. Machine learning algorithms determined that in rats, aggression is not a principal prognostic factor for dominant-submissive behavior. Alternatively, dominant-submissive behavior is determined solely by the rats' depressive-anxious state and exploratory activity. We expect the causal approach used in this study will guide future studies into mood conditions and behavioral changes following TBI.

Blood Glutamate Scavenging With Pyruvate as a Novel Preventative and Therapeutic Approach for Depressive-Like Behavior Following Traumatic Brain Injury in a Rat Model

Depression is a common and serious complication following traumatic brain injury (TBI). Both depression and TBI have independently been associated with pathologically elevated extracellular brain glutamate levels. In the setting of TBI, blood glutamate scavenging with pyruvate has been widely shown as an effective method to provide neuroprotection by reducing blood glutamate and subsequent brain glutamate levels. Here we evaluate pyruvate as a novel approach in the treatment and prevention of post-TBI depression-like behavior in a rat model. Rats were divided into five groups: (1) sham-operated control with pyruvate, (2) sham-operated control with placebo, (3) post-TBI with placebo, (4) post-TBI given preventative pyruvate, and (5) post-TBI treated with pyruvate. These groups had an equal number of females and males. Rats were assessed for depressive-like behavior, neurological status, and glutamate levels in the blood and brain. Post-TBI neurological deficits with concurrent elevations in glutamate levels were demonstrated, with peak glutamate levels 24 h after TBI. Following TBI, the administration of either prophylactic or therapeutic pyruvate led to reduced glutamate levels, improved neurologic recovery, and improved depressive-like behavior. Glutamate scavenging with pyruvate may be an effective prophylactic and therapeutic option for post-TBI depression by reducing associated elevations in brain glutamate levels.

Modulatory action of environmental enrichment on hormonal and behavioral responses induced by chronic stress in rats: Hypothalamic renin-angiotensin system components

Environmental enrichment (EE) has been studied as a protocol that can improve brain plasticity and may protect against negative insults such as chronic stress. The aim of this study was to evaluate the effects of EE on the hormonal and behavioral responses induced by chronic mild unpredictable stress (CMS) in rats, considering the involvement of the renin-angiotensin system. Male adult rats were divided into 4 groups: control, CMS, EE, and CMS + EE, and the experimental protocol lasted for 7 weeks. EE was performed during 7 weeks, 5 days per week, 2 h per day. CMS was applied during weeks 3, 4, and 5. After the CMS (week 6), depression-like behavior was evaluated by forced swimming and sucrose consumption tests, anxiety level was evaluated using the elevated plus-maze test, and memory was evaluated using the Y-maze test. On week 7, the animals were euthanized and basal plasma levels of corticosterone and catecholamines were determined. The hypothalamus was isolated and tissue levels of angiotensin peptides were evaluated. CMS increased plasma corticosterone, norepinephrine, and epinephrine basal concentrations, induced depression-like behaviors, impaired memory, and increased hypothalamic angiotensin I, II, and IV concentrations. EE decreased stress hormones secretion, depression-like behaviors, memory impairment, and hypothalamic angiotensin II induced by stress. Reductions of anxiety-like behavior and norepinephrine secretion were observed in both stressed and unstressed groups. The results indicated that EE seemed to protect adult rats against hormonal and behavioral CMS effects, and that the reduction of angiotensin II could contribute to these effects.