Differential susceptibility of cortical and subcortical inhibitory neurons and astrocytes in the long term following diffuse traumatic brain injury

Long‐term diffuse traumatic brain injury (dTBI) causes neuronal hyperexcitation in supragranular layers in sensory cortex, likely through reduced inhibition. Other forms of TBI affect inhibitory interneurons in subcortical areas but it is unknown if this occurs in cortex, or in any brain area in dTBI. We investigated dTBI effects on inhibitory neurons and astrocytes in somatosensory and motor cortex, and hippocampus, 8 weeks post‐TBI. Brains were labeled with antibodies against calbindin (CB), parvalbumin (PV), calretinin (CR) and neuropeptide Y (NPY), and somatostatin (SOM) and glial fibrillary acidic protein (GFAP), a marker for astrogliosis during neurodegeneration. Despite persistent behavioral deficits in rotarod performance up to the time of brain extraction (TBI = 73.13 ± 5.23% mean ± SEM, Sham = 92.29 ± 5.56%, P < 0.01), motor cortex showed only a significant increase, in NPY neurons in supragranular layers (mean cells/mm² ± SEM, Sham = 16 ± 0.971, TBI = 25 ± 1.51, P = 0.001). In somatosensory cortex, only CR⁺ neurons showed changes, being decreased in supragranular (TBI = 19 ± 1.18, Sham = 25 ± 1.10, P < 0.01) and increased in infragranular (TBI = 28 ± 1.35, Sham = 24 ± 1.07, P < 0.05) layers. Heterogeneous changes were seen in hippocampal staining: CB⁺ decreased in dentate gyrus (TBI = 2 ± 0.382, Sham = 4 ± 0.383, P < 0.01), PV⁺ increased in CA1 (TBI = 39 ± 1.26, Sham = 33 ± 1.69, P < 0.05) and CA2/3 (TBI = 26 ± 2.10, Sham = 20 ± 1.49, P < 0.05), and CR⁺ decreased in CA1 (TBI = 10 ± 1.02, Sham = 14 ± 1.14, P < 0.05). Astrogliosis significantly increased in corpus callosum (TBI = 6.7 ± 0.69, Sham = 2.5 ± 0.38; P = 0.007). While dTBI effects on inhibitory neurons appear region‐ and type‐specific, a common feature in all cases of decrease was that changes occurred in dendrite targeting interneurons involved in neuronal integration. J. Comp. Neurol. 524:3530–3560, 2016. © 2016 Wiley Periodicals, Inc.     

Magnetic resonance imaging of regional hemodynamic and cerebrovascular recovery after lateral fluid-percussion brain injury in rats

Hemodynamic and cerebrovascular factors are crucially involved in secondary damage after traumatic brain injury (TBI). With magnetic resonance imaging, this study aimed to quantify regional cerebral blood flow (CBF) by arterial spin labeling and cerebral blood volume by using an intravascular contrast agent, during 14 days after lateral fluid-percussion injury (LFPI) in rats. Immunohistochemical analysis of vessel density was used to evaluate the contribution of vascular damage. Results show widespread ipsilateral and contralateral hypoperfusion, including both the cortex and the hippocampus bilaterally, as well as the ipsilateral thalamus. Hemodynamic unrest may partly be explained by an increase in blood vessel density over a period of 2 weeks in the ipsilateral hippocampus and perilesional cortex. Furthermore, three phases of perilesional alterations in CBF, progressing from hypoperfusion to normal and back to hypoperfusion within 2 weeks were shown for the first time in a rat TBI model. These three phases were similar to hemodynamic fluctuations reported in TBI patients. This makes it feasible to use LFPI in rats to study mechanisms behind hemodynamic changes and to explore novel therapeutic approaches for secondary brain damage after TBI.     

Muscarinic cholinergic receptor binding in rat brain following traumatic brain injury

Recent evidence suggests that excessive activation of muscarinic cholinergic receptors (mAChRs) contributes significantly to the pathophysiological consequences of traumatic brain injury (TBI). To examine possible alterations in mAChRs after TBI, the affinity (K_d) and maximum number of binding sites (B_max) of mAChRs in hippocampus, neocortex, brain stem and cerebellum were determined by [³H]QNB binding. Three groups of rats were examined: 1 h post-TBI (n = 21), 24 h post-TBI (n = 21) and sham-injured rats (n = 21). K_d values were significantly higher in hippocampus and brain stem at 1 but not 24 h post-TBI compared with sham-injured controls (P < 0.05). K_d values did not significantly differ in neocortex and cerebellum at 1 or 24 h post-TBI compared with sham-injured controls. B_max values did not significantly differ in any brain areas at 1 or 24 h post-TBI compared with sham-injured controls These results show that TBI significantly decreases the affinity of mAChRs in hippocampus and brain stem at an early stage post-TBI, which may contribute to desensitization of mAChRs after TBI. The findings of no change in B_max values are consistent with a transient elevation in ACh concentrations after TBI.     

Neuronal and synaptic morphological alterations in the hippocampus of cannabinoid receptor type 1 knockout mice

Cannabinoid receptor type 1 (CB1R) modulates synaptic activity and is widely distributed in brain areas such as the hippocampus, cerebellum, cerebral cortex, and striatum, among others. CB1R is involved in processes such as memory, learning, motor coordination, and mood. Genetic deletion of CB1R causes behavioral alterations. In this work, we evaluated neuronal morphology and synaptic structure in the hippocampus of adult male CB1R knockout mice (CB1R^−/−). Morphological changes in the CB1R^−/− hippocampus evidenced a decrease in the expression of cytoskeletal proteins neurofilaments 160 KDa, neurofilaments 200 KDa, and microtubule-associated protein 2. CA1 neurons showed decreased arborization and changes in synaptic structure such as lower thickness of postsynaptic density and a reduction in synaptophysin levels. Results obtained in the present work provide evidence of the participation of CB1R in the establishment of neuronal structure and networks that could have an important role in neuronal plasticity. In addition, these changes observed in CB1R^−/− could be correlated with behavioral alterations reported.     

Selective plasticity of hippocampal GABAergic interneuron populations following kindling of different brain regions

The vulnerability and plasticity of hippocampal GABAergic interneurons is a topic of broad interest and debate in the field of epilepsy. In this experiment, we used the electrical kindling model of epilepsy to determine whether seizures that originate in different brain regions have differential effects on hippocampal interneuron subpopulations. Long‐Evans rats received 99 electrical stimulations of the hippocampus, amygdala, or caudate nucleus, followed by sacrifice and immunohistochemical or western blot analyses. We analyzed markers of dendritic (somatostatin), perisomatic (parvalbumin), and interneuron‐selective (calretinin) inhibition, as well as an overall indicator (GAD67) of interneuron distribution across all major hippocampal subfields. Our results indicate that kindling produces selective effects on the number and morphology of different functional classes of GABAergic interneurons. In particular, limbic kindling appears to enhance dendritic inhibition, indicated by a greater number of somatostatin‐immunoreactive (‐ir) cells in the CA1 pyramidal layer and robust morphological sprouting in the dentate gyrus. We also found a reduction in the number of interneuron‐selective calretinin‐ir cells in the dentate gyrus of hippocampal‐kindled rats, which suggests a possible reduction of synchronized dendritic inhibition. In contrast, perisomatic inhibition indicated by parvalbumin immunoreactivity appears to be largely resilient to the effects of kindling. Finally, we found a significant induction in the number of GAD67‐cells in caudate‐kindled rats in the dentate gyrus and CA3 hippocampal subfields. Taken together, our results demonstrate that kindling has subfield‐selective effects on the different functional classes of hippocampal GABAergic interneurons. J. Comp. Neurol. 525:389–406, 2017. © 2016 Wiley Periodicals, Inc.     

Greater neurodegeneration and behavioral deficits after single closed head traumatic brain injury in adolescent versus adult male mice

Traumatic brain injury (TBI) is a major public health concern affecting 2.8 million people per year in the United States, of whom about 1 million are children under 19 years old. Animal models of TBI have been developed and used in multiple ages of animals, but direct comparisons of adult and adolescent populations are rare. The current studies were undertaken to directly compare outcomes between adult and adolescent male mice, using a closed head, single-impact model of TBI. Six-week-old adolescent and 9-week-old adult male mice were subjected to mild–moderate TBI. Histological measures for neurodegeneration, gliosis, and microglial neuroinflammation, and behavioral tests of locomotion and memory were performed. Adolescent TBI mice have increased mortality (Χ² = 20.72, p < 0.001) compared to adults. There is also evidence of hippocampal neurodegeneration in adolescents that is not present in adults. Hippocampal neurodegeneration correlates with histologic activation of microglia, but not with increased astrogliosis. Adults and adolescents have similar locomotion deficits after TBI that recover by 16 days postinjury. Adolescents have memory deficits as evidenced by impaired novel object recognition between 3–4 and 4–16 days postinjury (F_1,26 = 5.23, p = 0.031) while adults do not. In conclusion, adults and adolescents within a close age range (6–9 weeks) respond to TBI differently. Adolescents are more severely affected by mortality, neurodegeneration, and inflammation in the hippocampus compared to adults. Adolescents, but not adults, have worse memory performance after TBI that lasts at least 16 days postinjury.     

A potential entanglement between the spinal cord and hippocampus: Theta rhythm correlates with neurogenesis deficiency following spinal cord injury in male rats

Cognitive deficits due to spinal cord injury (SCI) have been elucidated in both animals and humans with SCI. Such disorders may cause concomitant oscillatory changes in regions of the brain involving in cognition; a subject that has not been directed mechanistically. One of the crucial oscillations, having a prominent role in cognition, particularly spatial memory, is hippocampal theta rhythm. Our research revealed that SCI could induce changes not only in the neurogenesis and apoptosis rate of the hippocampus but also in theta power as well as receptors involving in the generation of this rhythm. Herein we used 24 male Wistar rats (Sham/SCI = 12) and examined the effect of spinal cord contusion on hippocampal theta rhythm, spatial memory, and neurodegeneration. We proved that SCI eliminates hippocampus-dependent theta power through spatial working memory, and correlates significantly with neurodegeneration and expression of receptors (NMDA, GABAA, Muscarinic1/M1), which are in turn essential in generation of theta rhythm. The immunohistochemistry analysis also demonstrated a significant decrease in DCX+ and BrdU+ cells; however, according to TUNEL assay, apoptosis is significantly higher in SCI-induced animals. The western blotting analysis further showed a significant reduction of the abovementioned receptors in the hippocampus. We also verified that SCI impairs the spatial memory, proved by poor performance in the Y-maze task. As well as, based on the local field potential recordings analysis, SCI decreases the power of theta rhythm. Eventually, this study demonstrated that chronic brain neurodegeneration occurs after SCI accompanied by theta rhythm and cognitive deficiency.     

Age-dependent release of high-mobility group box protein-1 and cellular neuroinflammation after traumatic brain injury in mice

Accumulating research suggests that children may be more vulnerable to poor long-term outcomes after traumatic brain injury (TBI) compared to adults. The neuroinflammatory response, known to contribute to neuropathology after TBI, appears to differ depending upon age-at-insult, although this response has not been well-characterized. Elevated levels of a key initiator of inflammation, high-mobility group box protein 1 (HMGB1), have been associated with worsened outcomes after TBI in young patients. This study therefore aimed to characterize the acute time course of key mediators of the inflammatory cascade, including HMGB1, after pediatric and adult TBI. Male C57Bl/6 mice were subjected to severe controlled cortical impact or a sham control surgery, at either early adulthood (8–10 weeks) or a pediatric age (3 weeks). Cortical tissue was collected for Western blot detection of astrocyte and microglial activation (GFAP and CD68) and HMGB1 at 2 hr, 6 hr, 24 hr, 3 days, and 7 days postinjury, and serum was collected for enzyme-linked immunoassays to quantify peripheral HMGB1. An additional cohort of brains was harvested at 3 day postinjury for immunofluorescence staining. Results demonstrated a temporal profile of CD68, GFAP, and HMGB1 after TBI relative to sham, which differed between the adult and pediatric cohorts. An increase in peripheral HMGB1 was found in serum from pediatric TBI mice, which was not evident in adult serum. Together, these findings demonstrate that HMGB1 and the downstream cellular inflammatory response are influenced by age-at-insult, which may be an important consideration for treatment strategies aiming to ameliorate this response after TBI.     

Comprehensive analysis of area‐specific and time‐dependent changes in gene expression in the motor cortex of macaque monkeys during recovery from spinal cord injury

The present study aimed to assess the molecular bases of cortical compensatory mechanisms following spinal cord injury in primates. To accomplish this, comprehensive changes in gene expression were investigated in the bilateral primary motor cortex (M1), dorsal premotor cortex (PMd), and ventral premotor cortex (PMv) after a unilateral lesion of the lateral corticospinal tract (l‐CST). At 2 weeks after the lesion, a large number of genes exhibited altered expression levels in the contralesional M1, which is directly linked to the lesioned l‐CST. Gene ontology and network analyses indicated that these changes in gene expression are involved in the atrophy and plasticity changes observed in neurons. Orchestrated gene expression changes were present when behavioral recovery was attained 3 months after the lesion, particularly among the bilateral premotor areas, and a large number of these genes are involved in plasticity. Moreover, several genes abundantly expressed in M1 of intact monkeys were upregulated in both the PMd and PMv after the l‐CST lesion. These area‐specific and time‐dependent changes in gene expression may underlie the molecular mechanisms of functional recovery following a lesion of the l‐CST.     

Expression of Kv3.1b potassium channel is widespread in macaque motor cortex pyramidal cells: A histological comparison between rat and macaque

There are substantial differences across species in the organization and function of the motor pathways. These differences extend to basic electrophysiological properties. Thus, in rat motor cortex, pyramidal cells have long duration action potentials, while in the macaque, some pyramidal neurons exhibit short duration “thin” spikes. These differences may be related to the expression of the fast potassium channel Kv3.1b, which in rat interneurons is associated with generation of thin spikes. Rat pyramidal cells typically lack these channels, while there are reports that they are present in macaque pyramids. Here we made a systematic, quantitative comparison of the Kv3.1b expression in sections from macaque and rat motor cortex, using two different antibodies (NeuroMab, Millipore). As our standard reference, we examined, in the same sections, Kv3.1b staining in parvalbumin‐positive interneurons, which show strong Kv3.1b immunoreactivity. In macaque motor cortex, a large sample of pyramidal neurons were nearly all found to express Kv3.1b in their soma membranes. These labeled neurons were identified as pyramidal based either by expression of SMI32 (a pyramidal marker), or by their shape and size, and lack of expression of parvalbumin (a marker for some classes of interneuron). Large (Betz cells), medium, and small pyramidal neurons all expressed Kv3.1b. In rat motor cortex, SMI32‐postive pyramidal neurons expressing Kv3.1b were very rare and weakly stained. Thus, there is a marked species difference in the immunoreactivity of Kv3.1b in pyramidal neurons, and this may be one of the factors explaining the pronounced electrophysiological differences between rat and macaque pyramidal neurons.     

Ferret brain possesses young interneuron collections equivalent to human postnatal migratory streams

The human early postnatal brain contains late migratory streams of immature interneurons that are directed to cortex and other focal brain regions. However, such migration is not observed in rodent brain, and whether other small animal models capture this aspect of human brain development is unclear. Here, we investigated whether the gyrencephalic ferret cortex possesses human-equivalent postnatal streams of doublecortin positive (DCX+) young neurons. We mapped DCX+ cells in the brains of ferrets at P20 (analogous to human term gestation), P40, P65, and P90. In addition to the rostral migratory stream, we identified three populations of young neurons with migratory morphology at P20 oriented toward: (a) prefrontal cortex, (b) dorsal posterior sigmoid gyrus, and (c) occipital lobe. These three neuronal collections were all present at P20 and became extinguished by P90 (equivalent to human postnatal age 2 years). DCX+ cells in such collections all expressed GAD67, identifying them as interneurons, and they variously expressed the subtype markers SP8 and secretagogin (SCGN). SCGN+ interneurons appeared in thick sections to be oriented from white matter toward multiple cortical regions, and persistent SCGN-expressing cells were observed in cortex. These findings indicate that ferret is a suitable animal model to study the human-relevant process of late postnatal cortical interneuron integration into multiple regions of cortex.     

Expression mapping,quantification, and complex formation of GluD1 and GluD2 glutamate receptors in adult mouse brain

In the cerebellum, GluD2 is exclusively expressed in Purkinje cells, where it regulates synapse formation and regeneration, synaptic plasticity, and motor learning. Delayed cognitive development in humans with GluD2 gene mutations suggests extracerebellar functions of GluD2. However, extracerebellar expression of GluD2 and its relationship with that of GluD1 are poorly understood. GluD2 mRNA and protein were widely detected, with relatively high levels observed in the olfactory glomerular layer, medial prefrontal cortex, cingulate cortex, retrosplenial granular cortex, olfactory tubercle, subiculum, striatum, lateral septum, anterodorsal thalamic nucleus, and arcuate hypothalamic nucleus. These regions were also enriched for GluD1, and many individual neurons coexpressed the two GluDs. In the retrosplenial granular cortex, GluD1 and GluD2 were selectively expressed at PSD-95-expressing glutamatergic synapses, and their coexpression on the same synapses was shown by SDS-digested freeze-fracture replica labeling. Biochemically, GluD1 and GluD2 formed coimmunoprecipitable complex formation in HEK293T cells and in the cerebral cortex and hippocampus. We further estimated the relative protein amount by quantitative immunoblotting using GluA2/GluD2 and GluA2/GluD1 chimeric proteins as standards for titration of GluD1 and GluD2 antibodies. Intriguingly, the relative amount of GluD2 was almost comparable to that of GluD1 in the postsynaptic density fraction prepared from the cerebral cortex and hippocampus. In contrast, GluD2 was overwhelmingly predominant in the cerebellum. Thus, we have determined the relative extracerebellar expression of GluD1 and GluD2 at regional, neuronal, and synaptic levels. These data provide a molecular–anatomical basis for possible competitive and cooperative interactions of GluD family members at synapses in various brain regions.     

A potential model of pediatric posttraumatic epilepsy

Preclinical models of pediatric posttraumatic epilepsy (PTE) are lacking. We hypothesized that traumatic brain injury (TBI), induced by controlled cortical impact, in immature rats would cause electroencephalographic (EEG) epileptiform activity and behavioral seizures. TBI or sham craniotomy was performed on postnatal day 17. Using video-EEG monitoring 4–11 months post-TBI, most TBI rats (87.5%) showed EEG spiking and one had spontaneous, recurrent seizures. Controls showed neither EEG spikes nor electrographic/behavioral seizures. Late seizures were rare after TBI, but EEG spiking was common and may represent a surrogate for PTE.     

Ubiquinol treatment for TBI in male rats: Effects on mitochondrial integrity,injury severity,and neurometabolism

Following traumatic brain injury (TBI), there is significant secondary damage to cerebral tissue from increased free radicals and impaired mitochondrial function. This imbalance between reactive oxygen species (ROS) production and the effectiveness of cellular antioxidant defenses is termed oxidative stress. Often there are insufficient antioxidants to scavenge ROS, leading to alterations in cerebral structure and function. Attenuating oxidative stress following a TBI by administering an antioxidant may decrease secondary brain injury, and currently many drugs and supplements are being investigated. We explored an over‐the‐counter supplement called ubiquinol (reduced form of coenzyme Q10), a potent antioxidant naturally produced in brain mitochondria. We administered intra‐arterial ubiquinol to rats to determine if it would reduce mitochondrial damage, apoptosis, and severity of a contusive TBI. Adult male F344 rats were randomly assigned to one of three groups: (1) Saline‐TBI, (2) ubiquinol 30 minutes before TBI (UB‐PreTBI), or (3) ubiquinol 30 minutes after TBI (UB‐PostTBI). We found when ubiquinol was administered before or after TBI, rats had an acute reduction in brain mitochondrial damage, apoptosis, and two serum biomarkers of TBI severity, glial fibrillary acidic protein (GFAP) and ubiquitin C‐terminal hydrolase‐L1 (UCH‐L1). However, in vivo neurometabolic assessment with proton magnetic resonance spectroscopy did not show attenuated injury‐induced changes. These findings are the first to show that ubiquinol preserves mitochondria and reduces cellular injury severity after TBI, and support further study of ubiquinol as a promising adjunct therapy for TBI.     

Mild carotid stenosis creates gradual,progressive, lifelong brain,and eye damage: An experimental laboratory rat model

In humans, carotid stenosis of 70% and above might be the cause of clinical symptoms such as transient ischemic attack and stroke. No clinical or animal studies have evaluated mild carotid occlusion, and few examined unilateral occlusion. Here, Westar rats underwent bilateral or unilateral carotid occlusion of 28–45%. Long-term effects were evaluated 9–11 months later. We conducted cognitive evaluation using spatial learning in a water maze and exploration behavior in an open field. Morphology of the brain was examined by MRI using diffusion-tensor imaging (DTI) and immunohistochemistry staining of the brain and eyes. Cognitive deficit was found in spatial memory and exploration behavior in both occluded groups. Brain and eyes histology presented severe damage in the bilateral group, compared to the unilateral one. DTI revealed an increase in mean diffusivity (MD) in the ventral thalamus and a decrease in fractional anisotropy in optic nerve and optic tract in bilateral rats, while unilateral rats showed only an increase in MD in the ventral pons. In those areas, a significant change in astrocytes, microglia, and number of apoptotic cells were found. Bilateral occlusion produced severe damage to both retinas, while unilateral occlusion produced damage mainly in the occluded side. We found that mild carotid stenosis, even in a unilateral occlusion, creates behavioral abnormalities presented by brain and eye histopathology. The results support our hypothesis that gradual formation of mild carotid stenosis along the life course leads to progressive damage that may create different degenerative diseases at a later age.     

Seizure frequency correlates with loss of dentate gyrus GABAergic neurons in a mouse model of temporal lobe epilepsy

Epilepsy occurs in one of 26 people. Temporal lobe epilepsy is common and can be difficult to treat effectively. It can develop after brain injuries that damage the hippocampus. Multiple pathophysiological mechanisms involving the hippocampal dentate gyrus have been proposed. This study evaluated a mouse model of temporal lobe epilepsy to test which pathological changes in the dentate gyrus correlate with seizure frequency and help prioritize potential mechanisms for further study. FVB mice (n = 127) that had experienced status epilepticus after systemic treatment with pilocarpine 31–61 days earlier were video‐monitored for spontaneous, convulsive seizures 9 hr/day every day for 24–36 days. Over 4,060 seizures were observed. Seizure frequency ranged from an average of one every 3.6 days to one every 2.1 hr. Hippocampal sections were processed for Nissl stain, Prox1‐immunocytochemistry, GluR2‐immunocytochemistry, Timm stain, glial fibrillary acidic protein‐immunocytochemistry, glutamic acid decarboxylase in situ hybridization, and parvalbumin‐immunocytochemistry. Stereological methods were used to measure hilar ectopic granule cells, mossy cells, mossy fiber sprouting, astrogliosis, and GABAergic interneurons. Seizure frequency was not significantly correlated with the generation of hilar ectopic granule cells, the number of mossy cells, the extent of mossy fiber sprouting, the extent of astrogliosis, or the number of GABAergic interneurons in the molecular layer or hilus. Seizure frequency significantly correlated with the loss of GABAergic interneurons in or adjacent to the granule cell layer, but not with the loss of parvalbumin‐positive interneurons. These findings prioritize the loss of granule cell layer interneurons for further testing as a potential cause of temporal lobe epilepsy.     

The effects of morphine and traumatic brain injury on central cholinergic neurons

This study examined the effects of morphine and fluid percussion traumatic brain injury (TBI) on the activity of cholinergic neurons in specific areas of the rat brain 12 min after injury. Acetylcholine (ACh) turnover, used as an index of cholinergic neuronal activity, was determined using gas chromatography-mass spectrometry. Although morphine administration alone in general did not significantly affect ACh content and turnover in specific brain areas, morphine administered prior to TBI either prevented injury-induced changes in ACh turnover (dorsal pontine tegmentum) or actually reduced the rate constant for ACh utilization (kACh) and the turnover rate of ACh (TRACh) following injury (thalamus, amygdala, cingulate/frontal cortex, and hippocampus). Thus, the protective effects of morphine against enduring behavioral deficits following TBI may involve the inhibition of central cholinergic neurons.     

Inhibition of Inducible Nitric Oxide Synthase Attenuates Deficits in Synaptic Plasticity and Brain Functions Following Traumatic Brain Injury

Traumatic brain injury (TBI), resulting from external force on the head, usually leads to long-term deficits in motor and cognitive functions. Inducible nitric oxide synthase (iNOS)-mediated excessive inflammation could exacerbate brain damage after TBI. The present study therefore investigated the potential neuroprotective effects of iNOS inhibition after TBI. Male C57BL/6J mice were subjected to controlled cortical impact injury and then treated with high selective iNOS inhibitor 1400W. Expression of iNOS mRNA was determined by quantitative RT-PCR. Western blotting was carried out to determine iNOS protein levels. Motor and cognitive functions, and long-term potentiation (LTP) in the medial prefrontal cortex (mPFC) and hippocampus were examined. Expression of iNOS was induced after TBI in a temporal manner. Treatment with 1400W after TBI improved motor and cognitive functions. TBI mice showed deficits in LTP in both the mPFC and hippocampus, and treatment with 1400W could rescue this impairment. Inhibition of iNOS attenuated deficits in synaptic plasticity and brain functions after TBI. The neuroprotective effect of iNOS inhibition on cognitive function might be via rescuing the TBI-induced LTP impairment.     

Outcome measures from experimental traumatic brain injury in male rats vary with the complete temporal biomechanical profile of the injury event

Millions suffer a traumatic brain injury (TBI) each year wherein the outcomes associated with injury can vary greatly between individuals. This study postulates that variations in each biomechanical parameter of a head trauma lead to differences in histological and behavioral outcome measures that should be considered collectively in assessing injury. While trauma severity typically scales with the magnitude of injury, much less is known about the effects of rate and duration of the mechanical insult. In this study, a newly developed voice-coil fluid percussion injury system was used to investigate the effects of injury rate and fluid percussion impulse on a collection of post-injury outcomes in male rats. Collectively the data suggest a potential shift in the specificity and progression of neuronal injury and function rather than a general scaling of injury severity. While a faster, shorter fluid percussion first presents as a mild TBI, neuronal loss and some behavioral tasks were similar among the slower and faster fluid percussion injuries. This study concludes that the sequelae of neuronal degeneration and behavioral outcomes are related to the complete temporal profile of the fluid percussion and do not scale only with peak pressure.