The Integrity of the Blood-Brain Barrier as a Critical Factor for Regulating Glutamate Levels in Traumatic Brain Injury.

A healthy blood-brain barrier (BBB) shields the brain from high concentrations of blood glutamate, which can cause neurotoxicity and neurodegeneration. It is believed that traumatic brain injury (TBI) causes long-term BBB disruption, subsequently increasing brain glutamate in the blood, in addition to increased glutamate resulting from the neuronal injury. Here, we investigate the relationship between blood and brain glutamate levels in the context of BBB permeability. Rats exposed to BBB disruption through an osmotic model or TBI and treated with intravenous glutamate or saline were compared to control rats with an intact BBB treated with intravenous glutamate or saline. After BBB disruption and glutamate administration, the concentrations of glutamate in the cerebrospinal fluid and blood and brain tissue were analyzed. The results showed a strong correlation between the brain and blood glutamate concentrations in the groups with BBB disruption. We conclude that a healthy BBB protects the brain from high levels of blood glutamate, and the permeability of the BBB is a vital component in regulating levels of glutamate in the brain. These findings bring a new approach to treating the consequences of TBI and other diseases where long-term disruption of the BBB is the central mechanism of their development.

Laser-Induced Brain Injury in the Motor Cortex of Rats.

A common technique for inducing stroke in experimental rodent models involves the transient (often denoted as MCAO-t) or permanent (designated as MCAO-p) occlusion of the middle cerebral artery (MCA) using a catheter. This generally accepted technique, however, has some limitations, thereby limiting its extensive use. Stroke induction by this method is often characterized by high variability in the localization and size of the ischemic area, periodical occurrences of hemorrhage, and high death rates. Also, the successful completion of any of the transient or permanent procedures requires expertise and often lasts for about 30 minutes. In this protocol, a laser irradiation technique is presented that can serve as an alternative method for inducing and studying brain injury in rodent models. When compared to rats in the control and MCAO groups, the brain injury by laser induction showed reduced variability in body temperature, infarct volume, brain edema, intracranial hemorrhage, and mortality. Furthermore, the use of a laser-induced injury caused damage to the brain tissues only in the motor cortex unlike in the MCAO experiments where destruction of both the motor cortex and striatal tissues is observed. Findings from this investigation suggest that laser irradiation could serve as an alternative and effective technique for inducing brain injury in the motor cortex. The method also shortens the time for completing the procedure and does not require expert handlers.

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.

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.

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.

Anesthetic Management of Patients with Congenital Insensitivity to Pain with Anhidrosis: A Retrospective Analysis of 358 Procedures Performed Under General Anesthesia.

BACKGROUND: Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive disorder characterized by recurrent episodic fevers, anhidrosis, absent reaction to noxious stimuli, self-mutilating behavior, and mental retardation. The anesthetic management of patients with CIPA is challenging. Autonomic nervous system abnormalities are common, and patients are at increased risk for perioperative complications. METHODS: In this study, we describe our experience with 35 patients with CIPA who underwent 358 procedures requiring general anesthesia between 1990 and 2013. RESULTS: During surgery, 3 patients developed hyperthermia intraoperatively (>37.5°C) without prior fever. There were no cases of intraoperative hyperpyrexia (>40°C). Aspiration was suspected in 2 patients, and in another patient aspiration was prevented by the use of endotracheal tube, early detection of regurgitation, and aggressive suctioning. One patient had cardiac arrest requiring cardiopulmonary resuscitation. Intraoperative bradycardia was observed in 10 cases, and postoperative bradycardia was observed in 11 cases. CONCLUSIONS: Regurgitation, hyperthermia, and aspiration were uncommon, but the incidence of bradycardia was higher than has been reported in previous studies. CIPA remains a challenge for anesthesiologists. Because of the rare nature of this disorder, the risk of various complications is difficult to predict.