A model of traumatic brain injury in rats is influenced by neuroprotection of diurnal variation which improves motor behavior and histopathology in white matter myelin

Traumatic brain injury (TBI) represents a significant public health concern and has been associated with high rates of morbidity and mortality. TBI generates two types of brain damage: primary and secondary. Secondary damage originates a series of pathophysiological processes, which include metabolic crisis, excitotoxicity, and neuroinflammation, which have deleterious consequences for neuronal function. However, neuroprotective mechanisms are also activated. The balance among these tissue responses, and its variations throughout the day determines the fate of the damage tissue. We have demonstrated less behavioral and morphological damage when a rat model of TBI was induced during the light hours of the day. Moreover, here we show that rats subjected to TBI in the dark lost less body weight than those subjected to TBI in the light, despite no change in food intake. Besides, the rats subjected to TBI in the dark had better performance in the beam walking test and presented less histological damage in the corpus callosum and the cingulum bundle, as shown by the Klüver-Barrera staining. Our results suggest that the time of day when the injury occurs is important. Thus, this data should be used to evaluate the pathophysiological processes of TBI events and develop better therapies.

Exposure to Sub-Lethal Doses of Permethrin Is Associated with Neurotoxicity: Changes in Bioenergetics, Redox Markers, Neuroinflammation and Morphology

Permethrin (PERM) is a member of the class I family of synthetic pyrethroids. Human use has shown that it affects different systems, with wide health dysfunctions. Our aim was to determine bioenergetics, neuroinflammation and morphology changes, as redox markers after subacute exposure to PERM in rats. We used MDA determination, protein carbonyl assay, mitochondrial O₂ consumption, expression of pro-inflammatory cytokines and a deep histopathological analysis of the hippocampus. PERM (150 mg/kg and 300 mg/kg body weight/day, o.v.) increased lipoperoxidation and carbonylated proteins in a dose-dependent manner in the brain regions. The activities of antioxidant enzymes glutathione peroxidase, reductase, S-transferase, catalase, and superoxide dismutase showed an increase in all the different brain areas, with dose-dependent effects in the cerebellum. Cytokine profiles (IL-1β, IL-6 and TNF-α) increased in a dose-dependent manner in different brain tissues. Exposure to 150 mg/kg of permethrin induced degenerated and/or dead neurons in the rat hippocampus and induced mitochondrial uncoupling and reduction of oxidative phosphorylation and significantly decreased the respiratory parameters state 3-associated respiration in complex I and II. PERM exposure at low doses induces reactive oxygen species production and imbalance in the enzymatic antioxidant system, increases gene expression of pro-inflammatory interleukins, and could lead to cell damage mediated by mitochondrial functional impairment.

Diurnal Variation Induces Neurobehavioral and Neuropathological Differences in a Rat Model of Traumatic Brain Injury

Traumatic brain injury (TBI) induces two types of brain damage: primary and secondary. Damage initiates a series of pathophysiological processes, such as metabolic crisis, excitotoxicity with oxidative stress-induced damage, and neuroinflammation. The long-term perpetuation of these processes has deleterious consequences for neuronal function. However, it remains to be elucidated further whether physiological variation in the brain microenvironment, depending on diurnal variations, influences the damage, and consequently, exerts a neuroprotective effect. Here, we established an experimental rat model of TBI and evaluated the effects of TBI induced at two different time points of the light–dark cycle. Behavioral responses were assessed using a 21-point neurobehavioral scale and the cylinder test. Morphological damage was assessed in different regions of the central nervous system. We found that rats that experienced a TBI during the dark hours had better behavioral performance than those injured during the light hours. Differences in behavioral performance correlated with less morphological damage in the perilesional zone. Moreover, certain brain areas (CA1 and dentate gyrus subregions of the hippocampus) were less prone to damage in rats that experienced a TBI during the dark hours. Our results suggest that diurnal variation is a crucial determinant of TBI outcome, and the hour of the day at which an injury occurs should be considered for future research.

Models used in the study of traumatic brain injury

Traumatic brain injury (TBI) is a contemporary health problem and a leading cause of mortality and morbidity worldwide. Survivors of TBI frequently experience disabling long-term changes in cognition, sensorimotor function, and personality. A crucial step in understanding TBI and providing better treatment has been the use of models to mimic the event under controlled conditions. Here, we describe the known head injury models, which can be classified as whole animal (in vivo), in vitro, and mathematical models. We will also review the ways in which these models have advanced the knowledge of TBI.

Diurnal variation of NMDA receptor expression in the rat cerebral cortex is associated with traumatic brain injury damage

OBJECTIVE

Data from our laboratory suggest that recovery from a traumatic brain injury depends on the time of day at which it occurred. In this study, we examined whether traumatic brain injury -induced damage is related to circadian variation in N-methyl-D-aspartate receptor expression in rat cortex.

RESULTS

We confirmed that traumatic brain injury recovery depended on the time of day at which the damage occurred. We also found that motor cortex N-methyl-D-aspartate receptor subunit NR1 expression exhibited diurnal variation in both control and traumatic brain injury-subjected rats. However, this rhythm is more pronounced in traumatic brain injury-subjected rats, with minimum expression in those injured during nighttime hours. These findings suggest that traumatic brain injury occurrence times should be considered in future clinical studies and when designing neuroprotective strategies for patients.

Effect of Intermediate-Frequency Repetitive Transcranial Magnetic Stimulation on Recovery following Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) represents a significant public health concern and has been associated with high rates of morbidity and mortality. Although several research groups have proposed the use of repetitive transcranial magnetic stimulation (rTMS) to enhance neuroprotection and recovery in patients with TBI, few studies have obtained sufficient evidence regarding its effects in this population. Therefore, we aimed to analyze the effect of intermediate-frequency rTMS (2 Hz) on behavioral and histological recovery following TBI in rats. Male Wistar rats were divided into six groups: three groups without TBI (no manipulation, movement restriction plus sham rTMS, and movement restriction plus rTMS) and three groups subjected to TBI (TBI only, TBI plus movement restriction and sham rTMS, and TBI plus movement restriction and rTMS). The movement restriction groups were included so that rTMS could be applied without anesthesia. Our results indicate that the restriction of movement and sham rTMS per se promotes recovery, as measured using a neurobehavioral scale, although rTMS was associated with faster and superior recovery. We also observed that TBI caused alterations in the CA1 and CA3 subregions of the hippocampus, which are partly restored by movement restriction and rTMS. Our findings indicated that movement restriction prevents damage caused by TBI and that intermediate-frequency rTMS promotes behavioral and histologic recovery after TBI.