Post-weaning Social Isolation in Male and Female Prairie Voles: Impacts on Central and Peripheral Immune System

The socially monogamous prairie vole (Microtus ochrogaster) offers a unique opportunity to examine the impacts of adolescent social isolation on the brain, immune system, and behavior. In the current study, male and female prairie voles were randomly assigned to be housed alone or with a same-sex cagemate after weaning (i.e., on postnatal day 21–22) for a 6-week period. Thereafter, subjects were tested for anxiety-like and depressive-like behaviors using the elevated plus maze (EPM) and Forced Swim Test (FST), respectively. Blood was collected to measure peripheral cytokine levels, and brain tissue was processed for microglial density in various brain regions, including the Nucleus Accumbens (NAcc), Medial Amygdala (MeA), Central Amygdala (CeA), Bed Nucleus of the Stria Terminalis (BNST), and Paraventricular Nucleus of the Hypothalamus (PVN). Sex differences were found in EPM and FST behaviors, where male voles had significantly lower total arm entries in the EPM as well as lower latency to immobility in the FST compared to females. A sex by treatment effect was found in peripheral IL-1β levels, where isolated males had a lower level of IL-1β compared to cohoused females. Post-weaning social isolation also altered microglial density in a brain region-specific manner. Isolated voles had higher microglial density in the NAcc, MeA, and CeA, but lower microglial density in the dorsal BNST. Cohoused male voles also had higher microglial density in the PVN compared to cohoused females. Taken together, these data suggest that post-weaning social housing environments can alter peripheral and central immune systems in prairie voles, highlighting a potential role for the immune system in shaping isolation-induced alterations to the brain and behavior.

Chronic High-frequency Stimulation of the Subthalamic Nucleus Induces a Sustained Inhibition of Serotonergic System via Loss of Cell Phenotype

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a standard treatment in Parkinson’s disease (PD). However, in a considerable number of patients debilitating psychiatric side-effects occur. Recent research has revealed that external stimuli can alter the neurotransmitters’ homeostasis in neurons, which is known as “neurotransmitter respecification”. Herein, we addressed if neurotransmitter respecification could be a mechanism by which DBS suppresses the serotonergic function in the dorsal raphe nucleus (DRN) leading to mood changes. We infused transgenic 5-HT-Cre (ePet-cre) mice with AAV viruses to achieve targeted expression of eYFP and the genetically encoded calcium indicator GCaMP6s in the DRN prior to methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. Mice received bilateral DBS electrodes in the STN and an optic fiber in the DRN for Ca2+ photometry. MPTP treated mice demonstrated behavioral and histological PD phenotype, whereas all STN-DBS animals exhibited an increased immobility time in the forced swim test, reduced Ca2+ activity, and loss of TPH2 expression in the DRN. Given the prominent role of Ca2+ transients in mediating neurotransmitter respecification, these results suggest a chronic loss of serotonergic phenotype in the DRN following STN-DBS. These findings indicate that loss of 5-HT cell phenotype may underlie the unwanted depressive symptoms following STN-DBS.

Nafamostat reduces systemic inflammation in TLR7-mediated virus-like illness

Background The serine protease inhibitor nafamostat has been proposed as a treatment for COVID-19, by inhibiting TMPRSS2-mediated viral cell entry. Nafamostat has been shown to have other, immunomodulatory effects, which may be beneficial for treatment, however animal models of ssRNA virus infection are lacking. In this study, we examined the potential of the dual TLR7/8 agonist R848 to mimic the host response to an ssRNA virus infection and the associated behavioural response. In addition, we evaluated the anti-inflammatory effects of nafamostat in this model. Methods CD-1 mice received an intraperitoneal injection of R848 (200 μg, prepared in DMSO, diluted 1:10 in saline) or diluted DMSO alone, and an intravenous injection of either nafamostat (100 μL, 3 mg/kg in 5% dextrose) or 5% dextrose alone. Sickness behaviour was determined by temperature, food intake, sucrose preference test, open field and forced swim test. Blood and fresh liver, lung and brain were collected 6 h post-challenge to measure markers of peripheral and central inflammation by blood analysis, immunohistochemistry and qPCR. Results R848 induced a robust inflammatory response, as evidenced by increased expression of TNF, IFN-γ, CXCL1 and CXCL10 in the liver, lung and brain, as well as a sickness behaviour phenotype. Exogenous administration of nafamostat suppressed the hepatic inflammatory response, significantly reducing TNF and IFN-γ expression, but had no effect on lung or brain cytokine production. R848 administration depleted circulating leukocytes, which was restored by nafamostat treatment. Conclusions Our data indicate that R848 administration provides a useful model of ssRNA virus infection, which induces inflammation in the periphery and CNS, and virus infection-like illness. In turn, we show that nafamostat has a systemic anti-inflammatory effect in the presence of the TLR7/8 agonist. Therefore, the results indicate that nafamostat has anti-inflammatory actions, beyond its ability to inhibit TMPRSS2, that might potentiate its anti-viral actions in pathologies such as COVID-19.

Saracatinib, a Src Tyrosine Kinase Inhibitor, as a Disease Modifier in the Rat DFP Model: Sex Differences, Neurobehavior, Gliosis, Neurodegeneration, and Nitro-Oxidative Stress

Diisopropylfluorophosphate (DFP), an organophosphate nerve agent (OPNA), exposure causes status epilepticus (SE) and epileptogenesis. In this study, we tested the protective effects of saracatinib (AZD0530), a Src kinase inhibitor, in mixed-sex or male-only Sprague Dawley rats exposed to 4–5 mg/kg DFP followed by 2 mg/kg atropine and 25 mg/kg 2-pralidoxime. Midazolam (3 mg/kg) was given to the mixed-sex cohort (1 h post-DFP) and male-only cohort (~30 min post-DFP). Saracatinib (20 mg/kg, oral, daily for 7 days) or vehicle was given two hours later and euthanized eight days or ten weeks post-DFP. Brain immunohistochemistry (IHC) showed increased microgliosis, astrogliosis, and neurodegeneration in DFP-treated animals. In the 10-week post-DFP male-only group, there were no significant differences between groups in the novel object recognition, Morris water maze, rotarod, or forced swim test. Brain IHC revealed significant mitigation by saracatinib in contrast to vehicle-treated DFP animals in microgliosis, astrogliosis, neurodegeneration, and nitro-oxidative stressors, such as inducible nitric oxide synthase, GP91phox, and 3-Nitrotyrosine. These findings suggest the protective effects of saracatinib on brain pathology seem to depend on the initial SE severity. Further studies on dose optimization, including extended treatment regimen depending on the SE severity, are required to determine its disease-modifying potential in OPNA models.

Evaluation of the Therapeutic Potential of Oral Phycocyanin-Rich Spirulina Extract in Neuropsychiatric Disorders.

Aim: Spirulina is a microalga that is widely used as a food supplement and is regarded as having performance enhancing and health promoting properties. We conducted a preliminary evaluation of the possible antidepressant, anti-anxiety, pro-socialization and cognition-enhancing effects of Spirulina in mouse models Methods: Sixty male BalbC mice aged 3 weeks were administered phycocyanin-rich Spirulina extract [PRSE, 545 mg/kg], fluoxetine [20 mg/kg] or water orally for 5 weeks. During the last 2 weeks of the experiment a series of behavioral-cognitive tests was performed to evaluate motor activity, antidepressant and anti-anxiety effects, socialization and cognitive effects. Effects of PRSE and fluoxetine were compared to those of water. Results: There was a significant effect of PRSE in the activity domain, manifesting as an increase in velocity in the open field [p=0.0007 vs. water]. Fluoxetine significantly enhanced immobility in the tail suspension test and the forced swim test reflecting the known antidepressant effect of this compound, but not PRSE. There were no significant effects of PRSE in tests of anxiety, socialization or cognition. Conclusions: The most striking observation in this study was that PRSE significantly enhanced activity in the open field test. Further studies are indicated to confirm and extend this finding and investigate possible mechanisms of action. The results of the current study do not support sporadic reports of possible antidepressant or cognition-enhancing effects of PRSE. Nevertheless, additional studies are indicated using depression models rather than naïve mice, alternative mouse strains, using additional cognitive tests, and administering higher PRSE doses.

Time to Abolish the Forced Swim Test in Rats for Depression Research?

The forced swim test (FST) is a controversial rodent test that has been used for decades, mainly in depression studies. The severity of the procedure makes it ethically questionable and its validity has also been questioned. In this paper we contribute new data to this debate. We identified original research papers related to Major Depressive Disorder (MDD), using rats as models. We compared the citations received by studies that used the FST and by studies that did not, within subsequent human medical papers. The results show that the number of citations received by both groups was very low, but in the papers describing the FST data the median citation number was zero. Citation analysis indicates that the FST is not contributing significantly to the understanding or cure of MDD. We briefly review other approaches that overcome the ethical limitations of the FST, and which might also surpass its efficacy.

Measurement of hemodynamic parameters and antidepressant activity in hypertensive rats following two weeks consumption of Acacia tortilis leaves extract

Background: Depression is common in hypertensive patients, and monotherapy may contribute for controlling depression in hypertensive patients and improving the socioeconomic outcomes. Previous studies have shown that Acacia tortilis possesses hypotensive activity. Objectives: Hence, the present study was planned to evaluate the hemodynamic activity and antidepressant effects of an ethanolic extract of Acacia tortilis leaves (ATEL) in salt-induced hypertensive rats. Methods: Sprague-Dawley rats were divided into 5 groups for experiments. The rats received respective treatment for 15 days: G1: Control (C); G2: Hypertensive control (HC: high dietary salt, 4% 10ml/kg); G3-5: HC+ ATEL (50, 100, 150mg/kg respectively). Cardiac hemodynamics (mean arterial blood pressure: MAP and heart rate: HR) were measured in the anaesthetized rats by an invasive method. For this method, one carotid artery was catheterized, a pressure catheter (pressure volume Millar microtip catheter connected to the Mikro-Tip Pressure-Volume System from Ultra Foundation Systems, PowerLab) was inserted, and the blood pressure (MAP in mm Hg) and HR (beats/min) were monitored continuously during the experiment. For the neuropharmacological studies, antidepressant activity was assessed by forced swim test on the 15th day. Results: A dose-dependent significant increase in mobility time was observed in rats (G3-5) treated with HC + different doses of ATEL (p < 0.05). However, the mobility time was significantly reduced by HC (G2) treatment compared with that of the control (p< 0.05). The hypertensive control (high dietary salt: HC) group showed significant increases in SP, DP, MAP, and HR (p<0.05) compared to the control (G1) group. At all doses (50, 100 and 150 mg/kg), MAP and HR were found to decrease significantly (p<0.05) when compared with the values in the HC (G2) group. Further analysis revealed an improvement in heart rate variability (HRV) in ATEL-treated hypertensive rats. Conclusion: The present research suggests that increased dietary salt intake not only increases blood pressure significantly but also increases depression. ATEL contains some efficacious constituents, N, N-dimethyltryptamine (DMT: a 5-HT1A agonist) with predominant antidepressant and antihypertensive activity. Hence, ATEL appears to be a valuable plant extract that can be useful, at least as an adjunct, for therapy in patients who suffer from both depression and hypertension. Objectives: Hence, the present study was planned to evaluate the hemodynamic activity and antidepressant effects of an ethanolic extract of Acacia tortilis leaves (ATEL) in salt-induced hypertensive rats. Methods: Sprague-Dawley rats were divided into 5 groups for experiments. The rats received respective treatment for 15 days: G1: Control (C); G2: Hypertensive control (HC: high dietary salt, 4% 10ml/kg); G3-5: HC+ ATEL (50, 100, 150mg/kg respectively). Cardiac hemodynamics (mean arterial blood pressure: MAP and heart rate: HR) were measured in the anaesthetized rats by an invasive method. For this method, one carotid artery was catheterized, a pressure catheter (pressure volume Millar microtip catheter connected to the Mikro-Tip Pressure-Volume System from Ultra Foundation Systems, PowerLab) was inserted, and the blood pressure (MAP in mm Hg) and HR (beats/min) were monitored continuously during the experiment. For the neuropharmacological studies, antidepressant activity was assessed by forced swim test on the 15th day. Results: A dose-dependent significant increase in mobility time was observed in rats (G3-5) treated with HC + different doses of ATEL (p < 0.05). However, the mobility time was significantly reduced by HC (G2) treatment compared with that of the control (p< 0.05). The hypertensive control (high dietary salt: HC) group showed significant increases in SP, DP, MAP, and HR (p<0.05) compared to the control (G1) group. At all doses (50, 100 and 150 mg/kg), MAP and HR were found to decrease significantly (p<0.05) when compared with the values in the HC (G2) group. Further analysis revealed an improvement in heart rate variability (HRV) in ATEL-treated hypertensive rats. Conclusion: The present research suggests that increased dietary salt intake not only increases blood pressure significantly but also increases depression. ATEL contains some efficacious constituents, N, N-dimethyltryptamine (DMT: a 5-HT1A agonist) with predominant antidepressant and antihypertensive activity. Hence, ATEL appears to be a valuable plant extract that can be useful, at least as an adjunct, for therapy in patients who suffer from both depression and hypertension.

Prevention of Stress-Induced Depressive-Like Behavior by Saffron Extract is Associated with Modulation of Kynurenine Pathway and Monoamine Neurotransmission

Depressive disorders are a major public health concern. Despite currently available treatment options, their prevalence steadily increases, and a high rate of therapeutic failure is often reported, together with important antidepressant-related side effects. This highlights the need to improve existing therapeutic strategies, including by using nutritional interventions. In that context, saffron recently received particular attention for its beneficial effects on mood, although the underlying mechanisms are poorly understood. This study investigated in mice the impact of a saffron extract (Safr’Inside™; 6.25 mg/kg, per os) on acute restraint stress (ARS)-induced depressive-like behavior and related neurobiological alterations, by focusing on hypothalamic–pituitary–adrenal axis, inflammation-related metabolic pathways, and monoaminergic systems, all known to be altered by stress and involved in depressive disorder pathophysiology. When given before stress onset, Safr’Inside administration attenuated ARS-induced depressive-like behavior in the forced swim test. Importantly, it concomitantly reversed several stress-induced monoamine dysregulations and modulated the expression of key enzymes of the kynurenine pathway, likely reducing kynurenine-related neurotoxicity. These results show that saffron pretreatment prevents the development of stress-induced depressive symptoms and improves our understanding about the underlying mechanisms, which is a central issue to validate the therapeutic relevance of nutritional interventions with saffron in depressed patients.