Establishing a 3-Tesla Magnetic Resonance Imaging Method for Assessing Diffuse Axonal Brain Injury in Rats.

Traumatic brain injury (TBI) significantly contributes to death and disability worldwide. However, treatment options remain limited. Here, we focus on a specific pathology of TBI, diffuse axonal brain injury (DABI), which describes the process of the tearing of nerve fibers in the brain after blunt injury. Most protocols to study DABI do not incorporate a specific model for that type of pathology, limiting their ability to identify mechanisms and comorbidities of DABI. In this study, we developed a magnetic resonance imaging (MRI) protocol for DABI in a rat model using a 3-T clinical scanner. We compared the neuroimaging outcomes with histologic and neurologic assessments. In a sample size of 10 rats in the sham group and 10 rats in the DABI group, we established neurological severity scores before the intervention and at 48 h following DABI induction. After the neurological evaluation after DABI, all rats underwent MRI scans and were subsequently euthanized for histological evaluation. As expected, the neurological assessment showed a high sensitivity for DABI lesions indicated using the ß-APP marker. Surprisingly, however, we found that the MRI method had greater sensitivity in assessing DABI lesions compared to histological methods. Out of the five MRI parameters with pathological changes in the DABI model, we found significant changes compared to sham rats in three parameters, and, as shown using comparative tests with other models, MRI was the most sensitive parameter, being even more sensitive than histology. We anticipate that this DABI protocol will have a significant impact on future TBI and DABI studies, advancing research on treatments specifically targeted towards improving patient quality of life and long-term outcomes.

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.

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.

Cerebral Venous Stenting for Pulsatile Tinnitus After Unsuccessful Jugular Ligation: Case Report and Literature Review.

Pulsatile tinnitus constitutes up to 10% of all tinnitus cases. Cerebral venous stenosis is a known etiology of pulsatile tinnitus. Treatment of pulsatile tinnitus secondary to venous stenosis with venous stenting has been reported in the literature but is not performed routinely. We would like to report a case of chronic pulsatile tinnitus treated with venous stent in a patient who previously underwent jugular vein ligation.

A Novel Histological Technique to Assess Severity of Traumatic Brain Injury in Rodents: Comparisons to Neuroimaging and Neurological Outcomes.

Here we evaluate an alternative protocol to histologically examine blood-brain barrier (BBB) breakdown, brain edema, and lesion volume following traumatic brain injury (TBI) in the same set of rodent brain samples. We further compare this novel histological technique to measurements determined by magnetic resonance imaging (MRI) and a neurological severity score (NSS). Sixty-six rats were randomly assigned to a sham-operated, mild TBI, moderate TBI, or severe TBI group. 48 h after TBI, NSS, MRI and histological techniques were performed to measure TBI severity outcome. Both the histological and MRI techniques were able to detect measurements of severity outcome, but histologically determined outcomes were more sensitive. The two most sensitive techniques for determining the degree of injury following TBI were NSS and histologically determined BBB breakdown. Our results demonstrate that BBB breakdown, brain edema, and lesion volume following TBI can be accurately measured by histological evaluation of the same set of brain samples.

A Comparison Between Pressure Wire and Microcatheter Measurements for Evaluating the Cerebral Venous Pressure Gradient.

Introduction: A pressure gradient of over 8 mm Hg across the stenosis (usually located in the transverse-sigmoid junction) is one of the criteria for cerebral venous stenting in idiopathic intracranial hypertension (IIH) patients. The possible inaccuracy of the traditional microcatheter-based pressure measurements has been discussed in previous studies. In the cardiology field, a dual-sensor pressure wire is routinely used for the evaluation of stenotic lesions. Using a pressure wire for cerebral vasculature was previously discussed in a small case series and case reports. In this study, we compared venous pressure measurements obtained using both a microcatheter and a pressure wire in patients who were candidates for stenting. Methods: A retrospective study was conducted, comparing the two methods of pressure measurements in 26 patients with venous stenosis. Altogether, 120 measurements were performed using both methods. Demographic characteristics, medical history, procedural details, medications, indications for the procedure, and complications were collected from the patient charts. Results: Based on an 8-mm Hg pressure gradient cutoff indication, 19 patients were found eligible to go through unilateral venous stenting based on catheter measurements alone. The wire results corroborated the catheter results in detecting all cases indicated for a stent. This finding implies a sensitivity equal to 100% for the wire measurements. There were no wire-related complications, demonstrating its safety. Conclusions: We conclude that the pressure wire is as safe as the microcatheter and can identify cases requiring intervention. A larger-scale study is needed to assess the measurement accuracy of the pressure wire in brain vasculature.

Adjunctive treatment with low dose intra-arterial eptifibatide and intravenous aspirin during carotid stenting: A case series.

PURPOSE: According to most guidelines, medical protocol for carotid stenting includes the administration of oral Aspirin and Clopidogrel at least four days before the procedure, with intraprocedural intravenous (IV) heparin. Some publications have also reported the safety of adding glycoprotein 2b/3a inhibitors to the protocol. In this retrospective study, we evaluate the safety of a new medication protocol that includes IV aspirin and intra-arterial Eptifibatide (glycoprotein 2b/3a inhibitor) during carotid stenting. All patients who underwent carotid stenting at Soroka University Medical Center between January 2015 and May 2020 were included (emergent cases were excluded). We divided patients into two groups-patients treated under the standard protocol, and patients treated under the new protocol. In the latter, patients received both the standard protocol regimen, as well as 150 mg IV aspirin immediately before stenting, and a slow intra-arterial injection of 2-3 mg Eptifibatide (glycoprotein 2b/3a antagonist) immediately after stenting. Forty-four patients were treated according to the standard protocol (group 1), and 41 patients were treated according to the new protocol (group 2). In group 1, six patients had complications, while in group 2, no complications of any kind were noted (p = 0.027). The safety and possible efficacy of this novel protocol was preliminarily demonstrated in the present study. Future studies are needed to prove the safety and efficacy of a specific drug regimen that will further reduce the complication rates of carotid stenting.

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.

The effect of pyruvate on the development and progression of post-stroke depression: A new therapeutic approach.

Post-stroke depression (PSD) is a common and serious complication following stroke. Both stroke and depression have independently been associated with pathologically elevated glutamate levels in the brain's extra-cerebral fluid (ECF). Here we evaluate an alternative therapeutic approach to PSD with pyruvate. Rats were randomly assigned into one of 3 groups: Middle Cerebral Artery Occlusion (MCAO) plus pyruvate treatment, MCAO plus placebo treatment, and sham operated rats. Post-MCAO depressive and anxiety-like behavior was assessed, along with neurological status, brain infarct zone, brain edema, blood brain barrier (BBB) breakdown, cerebrospinal fluid and blood glutamate levels. Anxiety-like behavior and levels of blood alanine and α-ketoglutarate were measured in naïve rats treated with pyruvate, as a control. Post-stroke neurological deficit with concurrent elevation in glutamate levels were demonstrated, with peak glutamate levels 24 h after MCAO. Treatment with pyruvate led to reduced glutamate levels 24 h after MCAO and improved neurologic recovery. Pyruvate treatment reduced lesion volume, brain edema and the extent of BBB permeability 24 h post-MCAO. Naïve rats treated with pyruvate showed increased levels of α-ketoglutarate. Rats demonstrated post-stroke depressive behavior that was improved by the administration of pyruvate. There was less anxiety-like behavior in post-stroke rats treated with placebo in comparison to the post-stroke rats treated with pyruvate or sham operated rats. Glutamate scavenging with pyruvate appears to be an effective as a method in providing neuroprotection following stroke and as a therapeutic option for the treatment of PSD by reducing the consequent elevations in CNS glutamate levels.

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.

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.