A Metric Test for Assessing Spatial Working Memory in Adult Rats following Traumatic Brain Injury.

Impairments to sensory, short-term, and long-term memory are common side effects after traumatic brain injury (TBI). Due to the ethical limitations of human studies, animal models provide suitable alternatives to test treatment methods, and to study the mechanisms and related complications of the condition. Experimental rodent models have historically been the most widely used due to their accessibility, low cost, reproducibility, and validated approaches. A metric test, which tests the ability to recall the placement of two objects at various distances and angles from one another, is a technique to study impairment in spatial working memory (SWM) after TBI. The significant advantages of metric tasks include the possibility of dynamic observation, low cost, reproducibility, relative ease of implementation, and low stress environment. Here, we present a metric test protocol to measure impairment of SWM in adult rats after TBI. This test provides a feasible way to evaluate physiology and pathophysiology of brain function more effectively.

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples.

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke involves middle cerebral artery occlusion (MCAO). Infarct zone, brain edema and blood-brain barrier (BBB) breakdown are measured as parameters that reflect the extent of brain injury after MCAO. A significant limitation to this method is that these measurements are normally obtained in different rat brain samples, leading to ethical and financial burdens due to the large number of rats that need to be euthanized for an appropriate sample size. Here we present a method to accurately assess brain injury following MCAO by measuring infarct zone, brain edema and BBB permeability in the same set of rat brains. This novel technique provides a more efficient way to evaluate the pathophysiology of stroke.

Inducing Acute Liver Injury in Rats via Carbon Tetrachloride (CCl4) Exposure Through an Orogastric Tube.

Acute liver injury (ALI) plays a crucial role in the development of hepatic failure, which is characterized by severe liver dysfunction including complications such as hepatic encephalopathy and impaired protein synthesis. Appropriate animal models are vital to test the mechanism and pathophysiology of ALI and investigate different hepatoprotective strategies. Due to its ability to perform chemical transformations, carbon tetrachloride (CCl4) is widely used in the liver to induce ALI through the formation of reactive oxygen species. CCl4 exposure can be performed intraperitoneally, by inhalation, or through a nasogastric or orogastric tube. Here, we describe a rodent model, in which ALI is induced by CCl4 exposure through an orogastric tube. This method is inexpensive, easily performed, and has minimal hazard risk. The model is highly reproducible and can be widely used to determine the efficacy of potential hepatoprotective strategies and assess markers of liver injury.

Induction of Diffuse Axonal Brain Injury in Rats Based on Rotational Acceleration.

Traumatic brain injury (TBI) is a major cause of death and disability. Diffuse axonal injury (DAI) is the predominant mechanism of injury in a large percentage of TBI patients requiring hospitalization. DAI involves widespread axonal damage from shaking, rotation or blast injury, leading to rapid axonal stretch injury and secondary axonal changes that are associated with a long-lasting impact on functional recovery. Historically, experimental models of DAI without focal injury have been difficult to design. Here we validate a simple, reproducible and reliable rodent model of DAI that causes widespread white matter damage without skull fractures or contusions.

A Novel Method for Assessing Cerebral Edema, Infarcted Zone and Blood-Brain Barrier Breakdown in a Single Post-stroke Rodent Brain.

Stroke is a major cause of global morbidity and mortality. Middle cerebral artery occlusion (MCAO) has historically been the most common animal model of simulating ischemic stroke. The extent of neurological injury after MCAO is typically measured by cerebral edema, infarct zone, and blood-brain barrier (BBB) permeability. A significant limitation of these methods is that separate sets of brains must be used for each measurement. Here we examine an alternative method of measuring cerebral edema, infarct zone and BBB permeability following MCAO in the same set of brain samples. Ninety-six rats were randomly divided into three experimental groups. Group 1 (n = 27) was used for the evaluation of infarct zone and brain edema in rats post-MCAO (n = 17) vs. sham-operated controls (n = 10). Group 2 (n = 27) was used for the evaluation of BBB breakdown in rats post-MCAO (n = 15) vs. sham-operated controls (n = 10). In Group 3 (n = 42), all three parameters were measured in the same set of brain slices in rats post-MCAO (n = 26) vs. sham-operated controls (n = 16). The effect of Evans blue on the accuracy of measuring infarct zone by 2,3,5-triphenyltetrazolium chloride (TTC) staining was determined by measuring infarct zone with and without an applied blue filter. The effects of various concentrations of TTC (0, 0.05, 0.35, 0.5, 1, and 2%) on the accuracy of measuring BBB permeability was also assessed. There was an increase in infarct volume (p < 0.01), brain edema (p < 0.01) and BBB breakdown (p < 0.01) in rats following MCAO compared to sham-operated controls, whether measured separately or together in the same set of brain samples. Evans blue had an effect on measuring infarct volume that was minimized by the application of a blue filter on scanned brain slices. There was no difference in the Evans blue extravasation index for the brain tissue samples without TTC compared to brain tissue samples incubated in TTC. Our results demonstrate that measuring cerebral edema, infarct zone and BBB permeability following MCAO can accurately be measured in the same set of brain samples.

A Middle Cerebral Artery Occlusion Technique for Inducing Post-stroke Depression in Rats.

Post-stroke depression (PSD) is the most recurrent of all psychiatric complications resulting from an ischemic stroke. A greater majority (about 60%) of all ischemic stroke patients suffer from PSD, a disorder considered to be an ischemic stroke-related precursor for increased death and degradation in health. The pathophysiology of PSD is still obscure. To study the mechanism of development and occurrence of PSD further, and to find out a therapy, we attempted to develop a new protocol that requires occluding the middle cerebral artery (MCA) via the internal carotid artery (ICA) in rats. This protocol describes a model of PSD induced in rats through the middle cerebral artery occlusion (MCAO). Also used in the experiment are the Porsolt forced swim test and the sucrose preference test to confirm and evaluate the depressive mood of the rats under investigation. Rather than inserting the catheter through the external carotid artery (ECA), as stipulated for the original procedure, this MCAO technique has the monofilament passing directly through the ICA. This MCAO technique was developed a few years ago and leads to a reduction in mortality and variability. It is generally accepted that the criteria used are preferred in the selection of biological models. The data obtained with this protocol show that this model of MCAO could be a way of inducing PSD in rats and could potentially lead to the understanding of the pathophysiology and the future development of new drugs and other neuroprotective agents.

Early life stress induces submissive behavior in adult rats.

Maternal-deprivation of rodent pups is a relevant model of extreme early-life stress that can be relevant to the understanding of long-term effects of war, migration, parental loss and displacement. Although even mild stress during infancy affects brain development and behavior, the current study focused on the effects of six hour daily maternal-separation, a model that reflects the severe distress often experienced in those circumstances. This study emphasizes the effect of maternal separation on social behavior in the context of a variety of factors that measure cognitive and emotional behavior which were subject to principle component analysis. Sprague-Dawley pups were separated from the dam for 6 h each day during the first 3-weeks of life and underwent a battery of behavioral tests at 3-months of age. We found that rodents exposed to postnatal maternal deprivation displayed submissive behavior in resident-intruder and dominant-submissive tests, as well as significantly more anxiety and anhedonia than control rats. The results of multivariate statistical analysis show that the dominant-submissive behavior correlates with depressive, anxiety and social behavior and can be predicted with an accuracy of 86.2%. The increased submissive behavior in male rats that had been subjected to severe postnatal stress suggests that exposure to stress during infancy and childhood could have long-term effects on social relationships. The mechanism of the long-term effects on depression, anxiety and submissive behavior requires further investigation.

An Alternative Model of Laser-Induced Stroke in the Motor Cortex of Rats.

BACKGROUND: A common experimental rodent model for stroke includes induction by a technique in which middle cerebral artery is transiently (MCAO-t) or permanently (MCAO-p) occluded by catheterization. However, this model has prominent disadvantages which consist of the high variability of localization and size of the ischemic area, cases of intracranial hemorrhage and high mortality. Furthermore, the duration of a single MCAO operation takes about thirty minutes and requires highly trained staff. In this article, we propose an alternative method, which is based on laser-induced stroke in the motor cortex. In our research, we compared the original MCAO-p and MCAO-t models and a novel laser model. RESULTS: Compared with the impact of original MCAO-p and MCAO-t technique on brain tissue, the minimally invasive laser model demonstrated a decrease in: variability in body temperature, percent of infarcted volume, blood brain barrier breakdown and brain edema, as well as a prominent decrease of mortality and intracranial hemorrhage. Among other findings of this article, it can be noted that damage to the brain tissue in laser groups occurred only in the region of the motor cortex, without involving the striatal area. CONCLUSIONS: The data presented in this paper show that the model of laser irradiation can serve as an effective method of inducible brain cortical infarction and may lead to a better understanding of the pathophysiology of ischemic stroke and the future development of new drugs and other neuro-protective agents.

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

BACKGROUND: Depression is common and results in a significant morbidity and economic burden. Depression is associated with pervasive impairments in social functioning, and antidepressant treatments are highly variable in improving these impairments. The objectives of this study were to test the effects of depression on social organization and behavior in a rodent model of depression, and to study the effectiveness of antidepressant medication in improving both symptoms of depression and the social function of depressed animals. METHODS: One hundred-twenty male Sprague-Dawley rats were randomly and equally divided between the control group and depression group. After induction of depression by 5 weeks of chronic unpredictable stress, rats received either antidepressant treatment or placebo. In parallel with the initiation of drug therapy, 20 social groups of six rats were subjected to the complex diving-for-food situation to evaluate their social functioning. Four behavioral tests evaluated symptoms of depression and anxiety at 3 different time points. RESULTS: We found that 1) depressed rats were significantly more active and aggressive in all parameters of social organization test compared with the control and antidepressant treatment groups, 2) depressed rats that received antidepressant treatment exhibited social behaviors like the control group, and 3) depression in the experimental groups was not accompanied by symptoms of anxiety. CONCLUSIONS: These results suggest that depression can significantly alter the social behavior and hierarchy in the social group in rats. Investigations of complex social group dynamics offer novel opportunities for translational studies of mood and psychiatric disorders.

Establishment of novel technical methods for evaluating brain edema and lesion volume in stroked rats: A standardization of measurement procedures.

Stroke plays a role in high morbidity and mortality. Deciphering its mechanisms and pathophysiology is critical for the creation of new drugs and therapies. Most of the previous animal models of stroke, aimed at identifying the extent and location of brain injury following stroke, require animal sacrifice, which, besides ethical considerations, also negates the ability for follow up studies with the same rats. Because of these failures, the use of clinical magnetic resonance scanners for evaluating small animal models has been increasing. Magnetic resonance imaging scanners used particularly for small-bore animals are eligible for use in high-resolution magnetic resonance imaging of rodent brains. However, high costs and scarcity factor heavily in the rare availability of these scanners. In our investigation, we sought to establish a unitary magnetic resonance imaging protocol for stroke assessment in rats. We made use of a 3-Tesla magnetic resonance imaging clinical scanner, as well as another clinical equipment, with the purpose of increasing its reproducibility. The results of inquest validated a new magnetic resonance imaging protocol, comparing a magnetic resonance imaging-measured infarcted zone to the "gold standard" of histological examination. We carried out the experimental procedure on a 3 Tesla magnetic resonance imaging clinical scanner using a conventional eight-channel receive-only coil. The two methods produced remarkable quantitative and qualitative correlations between them. Conclusively, we showed the clinical magnetic resonance imaging scanner to be a high-precision and sensitive image analysis instrument for evaluating both the infarct zone and the brain edema in a stroke experimental rat model.

Ultrasound-guided serratus anterior plane block for analgesia after thoracic surgery.

BACKGROUND: Patients who undergo surgical procedures that impair the integrity of the chest wall frequently experience extremely severe postoperative pain. Opiates and weaker analgesics, such as nonsteroidal anti-inflammatory drugs (NSAIDs), are not sufficiently effective in achieving control of severe pain and might cause respiratory and gastrointestinal complications. In the past decade, there has been an increased interest in the use of regional nerve blocks for post-thoracoscopy and post-thoracotomy analgesia. METHODS: This is a prospective, randomized, double-blind and single-center study. We recruited 104 patients who underwent elective thoracoscopy. Prior to surgery, the participating patients were randomized into one of two study groups: Group 1- the "standard control group" that received standard postoperative pain control with intravenous opioids, NSAIDs and acetaminophen (paracetamol) and Group 2- the "block group" that was treated by ultrasound-guided serratus anterior plane (SAP) block (a single injection of 0.25% bupivacaine hydrochloride 2 mg/kg plus dexamethasone 8 mg) with standard postoperative pain control regimen. We compared the clinical, laboratory, and postoperative pain assessment data of both groups. RESULTS: Patients in the SAP block Group 2 reported significantly lower levels of pain after thoracic surgery as assessed by their visual analog scale scores, as compared to the patients in the standard pain control Group 1 (P<0.001). The total dosage of morphine and tramadol required for pain relief during the first hours after surgery was significantly lower in the patients who received SAP block. Also, the incidence of vomiting after surgery was significantly lower among the patients who received SAP block than among the patients who received standard pain control. CONCLUSION: The results of the present study suggest that SAP block is an effective adjuvant treatment option for post-thoracic surgery analgesia. Compared to the current methods used for post-thoracic surgery pain relief, SAP block has some significant merits, particularly its ease of use and its low potential for side effects.

Biological and Behavioral Patterns of Post-Stroke Depression in Rats.

BACKGROUND: Post-stroke depression (PSD) is the most frequent psychiatric complication following ischemic stroke. It affects up to 60% of all patients and is associated with increased morbidity and mortality following ischemic stroke. The pathophysiology of PSD remains elusive and appears to be multifactorial, rather than "purely" biological or psychosocial in origin. Thus, valid animal models of PSD would contribute to the study of the etiology (and treatment) of this disorder. METHODS: The present study depicts a rat model for PSD, using middle cerebral artery occlusion (MCAO). The two-way shuttle avoidance task, Porsolt forced-swim test, and sucrose preference test were employed to assess any depression-like behavior. Localized brain expressions of brain-derived neurotrophic factor (BDNF) protein levels were evaluated to examine the possible involvement of the brain neuronal plasticity in the observed behavioral syndrome. The raw data were subjected to unsupervised fuzzy clustering (UFC) algorithms to assess the sensitivity of bio-behavioral measures indicative of depressive symptoms post MCAO. RESULTS: About 56% of the rats developed significant depressive-like behavioral disruptions as a result of MCAO compared with 4% in the sham-operated control rats. A pattern of a depressive-like behavioral response was common to all affected MCAO animals, characterized by significantly more escape failures and reduced number of total avoidance shuttles, a significant elevation in immobility duration, and reduced sucrose preference. Significant downregulations of BDNF protein levels in the hippocampal sub-regions, frontal cortex, and hypothalamus were observed in all affected MCAO animals. CONCLUSION: The UFC analysis supports the behavioral analysis and thus, lends validity to our results.

A New Method for Inducing a Depression-Like Behavior in Rats.

Contagious depression is a phenomenon that is yet to be fully recognized and this stems from insufficient material on the subject. At the moment, there is no existing format for studying the mechanism of action, prevention, containment, and treatment of contagious depression. The purpose of this study, therefore, was to establish the first animal model of contagious depression. Healthy rats can contract depressive behaviors if exposed to depressed rats. Depression is induced in rats by subjecting them to several manipulations of chronic unpredictable stress (CUS) over 5 weeks, as described in the protocol. A successful sucrose preference test confirmed the development of depression in the rats. The CUS-exposed rats were then caged with naïve rats from the contagion group (1 naïve rat/2 depressed rats in a cage) for an additional 5 weeks. 30 social groups were created from the combination of CUS-exposed rats and naïve rats. This proposed depression-contagion protocol in animals consists mainly of cohabiting CUS-exposed and healthy rats for 5 weeks. To ensure that this method works, a series of tests are carried out - first, the sucrose preference test upon inducing depression to rats, then, the sucrose preference test, alongside the open field and forced-swim tests at the end of the cohabitation period. Throughout the experiment, rats are given tags and are always returned to their cages after each test. A few limitations to this method are the weak differences recorded between the experimental and control groups in the sucrose preference test and the irreversible traumatic outcome of the forced swim test. These may be worth considering for suitability before any future application of the protocol. Nonetheless, following the experiment, naïve rats developed contagion depression after 5 weeks of sharing the same cage with the CUS-exposed rats.

Blood Glutamate Reducing Effect of Hemofiltration in Critically Ill Patients.

Glutamate toxicity plays a well-established role in secondary brain damage following acute and chronic brain insults. Previous studies have demonstrated the efficacy of hemodialysis and peritoneal dialysis in reducing blood glutamate levels. However, these methods are not viable options for hemodynamically unstable patients. Given more favorable hemodynamics, longer treatment, and less needed anticoagulation, we investigated whether hemofiltration could be effective in lowering blood glutamate levels. Blood samples were taken from 10 critically ill patients immediately before initiation of hemofiltration and after 1, 2, 4, 6, and 12 h, for a total of 6 blood samples. Samples were sent for determination of glutamate, glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), hemoglobin, hematocrit, urea, creatinine, glucose, sodium, potassium, platelet, and white blood cell (WBC) levels. There was a statistically significant reduction in blood glutamate levels at all time points compared to baseline levels. There was no difference in levels of GOT or GPT. Hemofiltration can be a promising method of reducing blood glutamate levels, especially in critically ill patients where hemodialysis and peritoneal dialysis may be contraindicated.

Establishment of an animal model of depression contagion.

BACKGROUND: Depression is a common and important cause of morbidity, and results in a significant economic burden. Recent human studies have demonstrated that that depression is contagious, and depression in family and friends might cumulatively increase the likelihood that a person will exhibit depressive behaviors. The mechanisms underlying contagion depression are poorly understood, and there are currently no animal models for this condition. METHODS: Rats were divided into 3 groups: depression group, contagion group, and control group. After induction of depression by 5 weeks of chronic unpredictable stress, rats from the contagion group were housed with the depressed rats (1 naïve rat with 2 depressed rats) for 5 weeks. Rats were then subjected to sucrose preference, open field, and forced swim tests. RESULTS: The sucrose preference was significantly reduced in the depressed rats (p<0.01) and contagion depression rats (p<0.01). Climbing time during forced swim test was reduced in the depression and contagion depression groups (p<0.001), whereas immobility time was significantly prolonged in only the depression group (p<0.001). Rats in both the depression (p<0.05) and depression contagion group (p<0.005) had decreased total travel distance and decreased mean velocity in the open field test, whereas the time spent in the central part was significantly shorter in only the depression group (p<0.001). CONCLUSIONS: In this study, for the first time we demonstrated depression contagion in an animal model. A reliable animal model may help better understand the underlying mechanisms of contagion depression, and may allow for future investigations of the studying therapeutic modalities.

Differential regulation of prostaglandin synthesis in neonatal rat microglia and astrocytes by somatostatin.

The aim of the present study was to investigate the role of somatostatin in the regulation of brain inflammation. We used lipopolysaccharide-induced prostaglandin E2 production in neonatal rat microglia and in astrocytes as a model of brain inflammation. Our data show an unexpected differential effect of somatostatin on lipopolysaccharide-induced prostaglandin E2 synthesis in rat microglia vs. in astrocytes. Somatostatin markedly inhibited the lipopolysaccharide-induced prostaglandin E2 synthesis in microglia whereas, on the contrary, in astrocytes the lipopolysaccharide-induced prostaglandin E2 production was actually enhanced by somatostatin. These novel observations imply that somatostatin may regulate brain inflammation in a dual manner.