Investigating the stress attenuating potential of furosemide in immobilization and electric foot-shock stress models in mice

Synergistic effects of combined therapy with cerebrolysin and enriched environment on anxiety-like behavior and spatial cognitive deficits in posttraumatic stress disorder-like mouse model

Posttraumatic stress disorder (PTSD) is a serious neuropsychiatric disorder that occurs after exposure to stressful, fearful, or troubling events. Cerebrolysin (CBL), consists of low molecular weights neurotrophic factors and amino acids obtained from purified porcine brain proteins. This study aimed to evaluate the possible therapeutic effects of enriched environment (EE) and CBL alone or combined for reducing anxiety and cognitive deficits in PTSD-like mouse models. For this purpose, inescapable electric foot shocks were delivered to Balb/c mice for two consecutive days. Then mice were treated with CBL (2.5 mL/kg) and/or were kept in EE (2 h per day) or received their combination for 14 consecutive days. The hole-board test and Lashley III paradigm were used to assess anxiety and spatial learning and memory, respectively. Changes in the serum corticosterone level and expression of synaptic elements, including; growth-associated protein 43, post-synaptic density 95, and synaptophysin were assessed in the hippocampus. This model caused anxiety and spatial memory impairment associated with increased serum corticosterone levels and decreased synaptic elements. Nevertheless, CBL and/or combination treatment could reverse behavioral and molecular alterations. Our findings indicated that CBL, separately or in combination with EE, is effective in reducing anxiety and spatial memory impairment in PTSD-like mice.

Investigations on Rho/ROCK signaling in post-traumatic stress disorder-like behavior in mice

Post-Traumatic Stress Disorder (PTSD) is a chronic condition that occurs in response to a traumatic event, and consequently, enhances the threat sensitivity. Rho/ROCK signaling has been implicated in the consolidation of fear memory, stress, depression, anxiety, and traumatic brain injury. However, its role in post-traumatic stress disorder remains elusive. Therefore, the present study was designed to explore the role of fasudil, a Rho/ROCK inhibitor, a mouse model of PTSD. Mice were subjected to underwater trauma stress followed by three situational reminders. Underwater trauma (UWT) significantly increased the freezing behavior, a marker of the formation of aversive memory, in response to situational reminders on the 3rd, 7th, and 14th days, suggesting the significant development of PTSD. Trauma and situational reminders were also associated with significant changes in behavioral parameters in open field, social interaction and actophotometer tests, along with a reduction in serum corticosterone levels. Fasudil (10 and 15 mg/kg) and sertraline (15 mg/kg), a standard drug for PTSD, significantly decreased the freezing behaviour in response to situational reminders, suggesting the inhibition of the formation of aversive fear memory. However, fasudil and sertraline did not modulate normal memory functions, as assessed on elevated plus maze test, before subjecting mice to traumatic stress. Treatment with fasudil and sertraline significantly restored the behavioral changes and normalized the corticosterone levels. Fasudil-mediated blockade of the Rho/ROCK pathway may be responsible for blocking the formation of aversive memory during the traumatic event, which may be manifested in form of decreased contextual fear response during situational reminders.

Different Synaptic Plasticity After Physiological and Psychological Stress in the Anterior Insular Cortex in an Observational Fear Mouse Model

Post-traumatic stress disorder (PTSD) can be triggered not only in people who have personally experienced traumatic events but also in those who witness them. Physiological and psychological stress can have different effects on neural activity, but little is known about the underlying mechanisms. There is ample evidence that the insular cortex, especially the anterior insular cortex (aIC), is critical to both the sensory and emotional experience of pain. It is therefore worthwhile to explore the effects of direct and indirect stress on the synaptic plasticity of the aIC. Here, we used a mouse model of observational fear to mimic direct suffering (Demonstrator, DM) and witnessing (Observer, OB) of traumatic events. After observational fear training, using a 64-channel recording system, we showed that both DM and OB mice exhibited a decreased ratio of paired-pulse with intervals of 50 ms in the superficial layers of the aIC but not in the deep layers. We found that theta-burst stimulation (TBS)–induced long-term potentiation (LTP) in OB mice was significantly higher than in DM mice, and the recruitment of synaptic responses occurred only in OB mice. Compared with naive mice, OB mice showed stronger recruitment and higher amplitude in the superficial layers of the aIC. We also used low-frequency stimulation (LFS) to induce long-term depression (LTD). OB mice showed greater LTD in both the superficial and deep layers of the aIC than naive mice, but no significant difference was found between OB and DM mice. These results provide insights into the changes in synaptic plasticity in the aIC after physiological and psychological stress, and suggest that different types of stress may have different mechanisms. Furthermore, identification of the possible causes of the differences in stress could help treat stress-related disorders.

Pharmacokinetic and pharmacodynamic evaluation of nasal liposome and nanoparticle based rivastigmine formulations in acute and chronic models of Alzheimer's disease

With the increasing aging population and progressive nature of the disease, Alzheimer's disease (AD) poses to be an oncoming epidemic with limited therapeutic strategies. It is characterized by memory loss, behavioral instability, impaired cognitive function, predominantly, cognitive inability manifested due to the accumulation of β-amyloid, with malfunctioned cholinergic system. Rivastigmine, a reversible dual cholinesterase inhibitor, is a more tolerable and widely used choice of drug for AD. However, rivastigmine being hydrophilic and undergoing the first-pass metabolism exhibits low CNS bioavailability. Nanoformulations including liposomes and PLGA nanoparticles can encapsulate hydrophilic drugs and deliver them efficiently to the brain. Besides, the nasal route is receiving considerable attention recently, due to its direct access to the brain. Therefore, the present study attempts to evaluate the pharmacokinetic and pharmacodynamic properties of nasal liposomal and PLGA nanoparticle formulations of rivastigmine in acute scopolamine-induced amnesia and chronic colchicine induced cognitive dysfunction animal models, and validate the best formulation by employing pharmacokinetic and pharmacodynamic (PK-PD) modeling. Nasal liposomal rivastigmine formulation showed the best pharmacokinetic features with rapid onset of action (Tmax = 5 min), higher Cmax (1489.5 ± 620.71), enhanced systemic bioavailability (F = 118.65 ± 23.54; AUC = 35,921.75 ± 9559.46), increased half-life (30.92 ± 8.38 min), and reduced clearance rate (Kel (1/min) = 0.0224 ± 0.006) compared to oral rivastigmine (Tmax = 15 min; Cmax = 56.29 ± 27.05; F = 4.39 ± 1.82; AUC = 1663.79 ± 813.54; t1/2 = 13.48 ± 5.79; Kel (1/min) = 0.0514 ± 0.023). Further, the liposomal formulation significantly rescued the memory deficit induced by scopolamine as well as colchicine superior to other formulations as assessed in Morris water maze and passive avoidance tasks. PK-PD modeling demonstrated a strong correlation between the pharmacokinetic parameters and acetylcholinesterase inhibition of liposomal formulation.

The Effects of Furosemide on Behavioral and Hormonal Parameters in Male and Female Mice Subjected to Immobilization and Cold-Water Stress

Introduction

The diuretic agent furosemide (FUR, 25 and 50 mg/kg) has been shown in a single report to act as an anti-stressor agent in two models of acute stress in mice, viz. electric foot-shock stress and immobilization (IMS). The present work aimed to investigate the possible anti-stressor action of FUR on two models of acute stress in mice, cold-water stress (CWS) and IMS, and tried to determine whether gender has any impact on the effect of FUR.

Methods

FUR (40 mg/kg) was injected intraperitoneally, and after 30 minutes, mice were subjected to CWS (4°C for three minutes) or IMS (fixing movement for two and a half hrs using adhesive tape). Motor and exploratory activities, neuromuscular coordination, and thermal nociception were then tested. Blood was collected from the mice and used to measure the concentrations of three stress hormones (corticosterone, epinephrine and prolactin).

Results

Mice subjected to CWS and IMS had significantly reduced motor and exploratory activities, neuromuscular coordination, and increased nociception. CWS and IMS also significantly increased the plasma concentrations of the three hormones. FUR pretreatment significantly mitigated these stress-induced hormonal changes. There was no significant sex difference when CWS or IMS was applied.

Discussion

IMS and CWS stimuli in male and female mice caused significant elevations in the plasma concentrations of corticosterone, epinephrine, and prolactin, accompanied by a significant reduction of motor and exploratory activities, neuromuscular coordination, and thermal nociception. There were no sex differences when IMS was applied. In stressed mice, prior administration of FUR (40 mg/kg) significantly decreased the concentrations of stress hormones, and this effect significantly mitigated the stress-induced behavioural and motor changes.

Exploring the anti-stress effects of imatinib and tetrabenazine in cold-water immersion-induced acute stress in mice

The aim of the present study was to explore the ameliorative role of imatinib and tetrabenazine in acute stress-induced behavioural and biochemical changes in mice. Cold-water immersion (5 min duration) was employed to induce acute stress and the resulting changes in the locomotor activity, exploratory behaviour, motor activity and social behaviour were assessed using the actophotometer, the hole board, the open field and the social interaction tests. The biochemical alterations were assessed by measuring the plasma corticosterone levels using ELISA kit. Cold-water immersion-induced acute stress diminished the locomotor activity, exploratory behaviour, motor activity and social behaviour along with increase in the plasma corticosterone levels. Administration of imatinib (50 and 100 mg/kg, i.p.), a tyrosine kinase inhibitor, significantly attenuated the cold-water immersion-induced behavioural alterations with normalization of the plasma corticosterone levels in a dose-dependent manner. Moreover, administration of tetrabenazine (1 and 2 mg/kg, i.p.), a vesicular monoamine transporter 2 (VMAT2) inhibitor, also abolished the acute stress-induced behavioural and biochemical changes in a dose-dependent manner. The beneficial effects of imatinib and tetrabenazine in normalizing acute stress-induced biochemical and behavioural changes make them promising therapeutic agents in the treatment of acute stress-related problems.

Investigating the role of nitric oxide in stress adaptive process in electric foot shock stress-subjected mice

AIM

The present study was designed to investigate the role of nitric oxide (NO) in the non-development of stress adaptation in high-intensity foot-shock stress (HIFS) subjected mice.

METHODS

Mice were subjected to low-intensity shocks (LIFS i.e. 0.5 mA) or HIFS (1.5 mA) for 5 days. Stress-induced behavioral changes were assessed by actophotometer, hole board, open field and social interaction tests. Biochemically, the serum corticosterone levels were measured as a marker of stress. L-arginine (100 mg/kg and 300 mg/kg), as NO donor, and L-NAME (10 mg/kg and 30 mg/kg), as nitric oxide synthase (NOS) inhibitor, were employed as pharmacological agents.

RESULTS

A single exposure of LIFS and HIFS produced behavioral and biochemical alterations. However, there was the restoration of behavioral and biochemical alterations on 5^th day in response to repeated LIFS exposure suggesting the development of stress adaptation. However, no stress adaptation was observed in HIFS subjected mice. Administration of L-arginine (300 mg/kg) abolished the stress adaptive response in LIFS-subjected mice, while L-NAME (30 mg/kg) induced the development of stress adaptation in HIFS subjected mice.

CONCLUSION

It is concluded that an increase in the NO release may possibly impede the process of stress adaptation in HIFS-subjected mice.

H3K4 dimethylation at FosB promoter in the striatum of chronic stressed rats promotes morphine-induced conditioned place preference

Expression of FosB gene in striatum is essential in addiction establishment. Activated glucocorticoid receptors (GRs) induce FosB gene expression in response to stressor. Therefore, elevation of FosB expression in striatum serves as one mechanism by which stress increases risk for addiction. In this study, adult male Sprague-Dawley rats were used to investigate whether chronic stress result in histone modifications at FosB gene promoter in striatum and how these histone modifications affect FosB expression and the establishment of addiction behavior after administration of drugs of abuse. Animals were randomly assigned to three groups: Electric foot shock (EFS) group received 7-day EFS to induce chronic stress; electric foot shock plus mifepristone (EFS + Mif) group were injected with mifepristone, a nonspecific GRs antagonist, before EFS; control group did not receive any EFS. All groups then received 2-day conditioned place preference (CPP) training with morphine (5 mg/kg body weight) to test vulnerability to drug addiction. Before and after morphine administration, FosB mRNA in striatum was quantified by real-time RT-PCR. Levels of histone H3/H4 acetylation and histone H3K4 dimethylation at FosB promoter in striatum after morphine administration were measured by using chromatin immunoprecipitation (ChIP) plus real-time PCR. EFS group had stronger place preference to morphine and had significantly higher level of FosB mRNA in striatum than the other two groups. H3K4 dimethylation was 2.6-fold higher in EFS group than control group, while no statistical difference in H3/H4 acetylation. Mifepristone administration before EFS decreased histone H3K4 dimethylation and FosB mRNA in striatum, and also diminished morphine-induced conditioned place preference. Altogether, increased level of H3K4 dimethylation at FosB promoter in striatum is partially dependent on the activation of GR and responsible for the elevated level of morphine-induced FosB mRNA in chronic stressed animals.