Novel pharmacologic therapies in the treatment of experimental traumatic brain injury: a review

Translational neurochemical research in acute human brain injury: the current status and potential future for cerebral microdialysis

Microdialysis (MD) was introduced as an intracerebral sampling method for clinical neurosurgery by Hillered et al. and Meyerson et al. in 1990. Since then MD has been embraced as a research tool to measure the neurochemistry of acute human brain injury and epilepsy. In general investigators have focused their attention to relative chemical changes during neurointensive care, operative procedures, and epileptic seizure activity. This initial excitement surrounding this technology has subsided over the years due to concerns about the amount of tissue sampled and the complicated issues related to quantification. The interpretation of mild to moderate MD fluctuations in general remains an issue relating to dynamic changes of the architecture and size of the interstitial space, blood-brain barrier (BBB) function, and analytical imprecision, calling for additional validation studies and new methods to control for in vivo recovery variations. Consequently, the use of this methodology to influence clinical decisions regarding the care of patients has been restricted to a few institutions. Clinical studies have provided ample evidence that intracerebral MD monitoring is useful for the detection of overt adverse neurochemical conditions involving hypoxia/ischemia and seizure activity in subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), thromboembolic stroke, and epilepsy. There is some data strongly suggesting that MD changes precede the onset of secondary neurological deterioration following SAH, hemispheric stroke, and surges of increased ICP in fulminant hepatic failure. These promising investigations have relied on MD-markers for disturbed glucose metabolism (glucose, lactate, and pyruvate) and amino acids. Others have focused on trying to capture other important neurochemical events, such as excitotoxicity, cell membrane degradation, reactive oxygen species (ROS) and nitric oxide (NO) formation, cellular edema, and BBB dysfunction. However, these other applications need additional validation. Although these cerebral events and their corresponding changes in neurochemistry are important, other promising MD applications, as yet less explored, comprise local neurochemical provocations, drug penetration to the human brain, MD as a tool in clinical drug trials, and for studying the proteomics of acute human brain injury. Nevertheless, MD has provided new important insights into the neurochemistry of acute human brain injury. It remains one of very few methods for neurochemical measurements in the interstitial compartment of the human brain and will continue to be a valuable translational research tool for the future. Therefore, this technology has the potential of becoming an established part of multimodality neuro-ICU monitoring, contributing unique information about the acute brain injury process. However, in order to reach this stage, several issues related to quantification and bedside presentation of MD data, implantation strategies, and quality assurance need to be resolved. The future success of MD as a diagnostic tool in clinical neurosurgery depends heavily on the choice of biomarkers, their sensitivity, specificity, and predictive value for secondary neurochemical events, and the availability of practical bedside methods for chemical analysis of the individual markers. The purpose of this review was to summarize the results of clinical studies using cerebral MD in neurosurgical patients and to discuss the current status of MD as a potential method for use in clinical decision-making. The approach was to focus on adverse neurochemical conditions in the injured human brain and the MD biomarkers used to study those events. Methodological issues that appeared critical for the future success of MD as a routine intracerebral sampling method were addressed.

Factors Associated with Neurological Outcome and Lesion Progression in Traumatic Subarachnoid Hemorrhage Patients

OBJECTIVE:

Traumatic subarachnoid hemorrhage (tSAH) is a frequent finding after closed-head injuries, and its presence is a powerful factor associated with poor outcome. The exact mechanism linking tSAH and an adverse outcome is poorly understood. The aim of this study was to identify the factors that may predict outcomes and changes in the computed tomographic (CT) scans of lesions in a selected population of tSAH patients.

METHODS:

We evaluated 141 patients admitted consecutively from January 1, 1997, to January 31, 1999, with a CT diagnosis of tSAH. The admission and “worst” CT scans were recorded. CT scan changes were reported as “significant CT progression” (changes in the Marshall classification) or “any CT progression.” The amount of subarachnoid blood was recorded using a modified Fisher classification. Outcome was assessed at 6 months after injury with the Glasgow Outcome Scale.

RESULTS:

Twenty-eight patients (19.9%) had an unfavorable Glasgow Outcome Scale outcome. In the univariate analysis, prognosis was significantly related to age, admission Glasgow Coma Scale score, Marshall CT classification score at admission and on the worst CT scan, amount of tSAH, and volume of the associated brain contusions. From multivariate analysis, the only factors independently related to outcome were the Glasgow Coma Scale score (P < 0.01) and size of the tSAH at admission (P < 0.001). Thirty-four patients (24.1%) had significant CT lesion progression, and 66 patients (46.8%) had some lesion progression. Patients having significant progression of the lesion had a higher risk of an unfavorable outcome (32 versus 10%; P = 0.004). Unadjusted factors predicting CT progression were the Glasgow Coma Scale score at admission, the Marshall classification at admission, the amount of subarachnoid blood, and the presence or volume of associated brain contusions at admission. Independent factors associated with significant CT progression were the amount of tSAH (P < 0.001) and the presence or volume of brain contusions at admission (P < 0.001).

CONCLUSION:

The outcome of patients with tSAH at admission is related in a logistic regression analysis to the admission Glasgow Coma Scale score and to the amount of subarachnoid blood. These patients also have a significant risk of CT progression. The amount of subarachnoid blood and the presence of associated parenchymal damage are powerful independent factors associated with CT progression, thus linking poor outcomes and CT changes.

Proteins released from degenerating neurons are surrogate markers for acute brain damage

The experimental and clinical study of degenerative brain disorders would benefit from new surrogate markers for brain damage. To identify novel candidate markers for acute brain injury, we report that rat cortical neurons release over 60 cytoskeletal and other proteins, as well as their proteolytic fragments into the medium during neuronal death. The profiles of released proteins differ for necrosis and apoptosis, although a subset of proteins is released generally during neurodegeneration. The value of this approach was established by immunodetection of the released proteins 14-3-3 zeta and 14-3-3 beta, as well as calpain and caspase derivatives of tau and alpha-spectrin in cerebrospinal fluid (CSF) following traumatic brain injury (TBI) or transient forebrain ischemia in the rat. These results indicate that proteins and their proteolytic fragments released from degenerating neurons are cerebrospinal fluid markers for acute brain damage and suggest that efflux of proteins from the injured brain may reflect underlying mechanisms for neurodegeneration.

Neuroprotection in ophthalmology: a review

Evidence has accumulated that damaged neural cells may not inevitably degenerate, and that in vivo cells which are not directly injured by an insult may be adversely affected by adjacent dying cells. Neuroprotection is a strategy which aims to maximize recovery of injured neural cells and minimize secondary damage to neighboring cells. In this work, we review the current knowledge from neuroprotection research using in vitro and animal models of eye diseases, and clinical data.

Hyperglycolysis is exacerbated after traumatic brain injury with fentanyl vs. isoflurane anesthesia in rats

Despite common use of narcotics in the clinical management of severe traumatic brain injury (TBI), in experimental models rats treated with fentanyl have exhibited worse functional outcome and more CA1 hippocampal death than rats treated with standard isoflurane anesthesia. We hypothesized that greater post-traumatic excitotoxicity, reflected by cerebral glucose utilization (CMRglu), may account for detrimental effects of fentanyl vs. isoflurane. Rats were anesthetized with either isoflurane (1% by inhalation) or fentanyl (10 mcg/kg iv bolus then 50 mcg/kg/h infusion). 14C-deoxyglucose autoradiography was performed 45 min after controlled cortical impact (CCI) to left parietal cortex (n=4 per anesthetic group) or in uninjured rats after 45 min of anesthesia (n=3 per anesthetic group). Uninjured rats treated with fentanyl vs. isoflurane showed 35-45% higher CMRglu in all brain structures (p<0.05) except CA3. After TBI in rats treated with isoflurane, CMRglu increased significantly only in ipsilateral CA1 and ipsilateral parietal cortex (p<0.05 vs. isoflurane uninjured). Conversely, after TBI in rats treated with fentanyl, CMRglu increased markedly and bilaterally in CA1 and CA3 (p<0.05 vs. fentanyl uninjured), but not ipsilateral parietal cortex. In contralateral CA1, CMRglu was nearly two times greater after TBI in fentanyl vs. isoflurane treated rats (p<0.05). Hyperglycolysis was exacerbated in CA1 and CA3 hippocampus after TBI in rats treated with fentanyl vs. isoflurane anesthesia. This post-traumatic hyperglycolysis suggests greater excitotoxicity and concurs with reports of worse functional outcome and more CA1 hippocampal death after TBI with fentanyl vs. isoflurane anesthesia.

PTK, ERK and p38 MAPK contribute to impaired NMDA-induced vasodilation after brain injury

N-Methyl-D-aspartate (NMDA)-induced pial artery dilation is reversed to vasoconstriction following fluid percussion brain injury (FPI). This study investigated the contribution of activation of protein tyrosine kinase (PTK) and the extracellular signal-regulated kinase (ERK) and p38 isoforms of mitogen-activated protein kinase (MAPK) in impaired vasodilation to NMDA after fluid percussion brain injury in pigs equipped with a closed cranial window. NMDA (10(-8), 10(-6) M)-induced vasodilation was reversed to vasoconstriction following fluid percussion brain injury, but such responses were partially restored by genistein (4',5,7-trihydroxy isoflavone), U0126 [1,4-diamino-2,3-dicyano-1,4-bis (0-aminophenylmercapto)butadiene] and SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole], PTK, ERK and p38 MAPK inhibitors (9+/-1% and 16+/-1%, sham control; -6+/-2% and -11+/-3%, fluid percussion brain injury; and 3+/-1% and 6+/-1%, fluid percussion brain injury-genistein, respectively). However, the robustness of the protection to NMDA dilation was significantly greater for U0126 vs. SB203580 (4+/-1% and 7+/-1% vs. 1+/-1% and 1+/-2%). Similar results were observed for glutamate. These data show that PTK, ERK and p38 MAPK activation contribute to impaired NMDA cerebrovasodilation after fluid percussion brain injury. These data suggest that activation of the ERK isoform of MAPK contributes to such impairment more than the p38 MAPK isoform.

Traumatic brain injury in infants and children: mechanisms of secondary damage and treatment in the intensive care unit

Unfortunately no specific pharmacologic therapies are available for the treatment of TBI in patients. Current investigation of contemporary therapies for the treatment of TBI consists of recycling of previously tested therapies in the era of contemporary neurointensive care. These therapies include hypothermia, decompressive craniectomy, osmotherapy, and controlled hyperventilation. It is hoped that more detailed knowledge regarding the dominant pathophysiologic mechanisms associated with TBI-excitotoxicity, CBF dysregulation, oxidative stress, and programmed cell death-will catapult an efficacious intervention from the laboratory bench to the bedside. This intervention may be a potent agent targeting a single dominant pathway, a broad-spectrum intervention such as hypothermia, or, more likely, a combination of therapies. Meanwhile, practitioners must offer meticulous supportive neurointensive care using clinically proven therapies aimed at minimizing cerebral swelling for the management of pediatric patients who are victims of TBI.

Poly(ADP-Ribose) polymerase-1 in acute neuronal death and inflammation: a strategy for neuroprotection

Poly(ADP-ribose) polymerase-1 (PARP-1) is an abundant nuclear enzyme that is activated primarily by DNA damage. Upon activation, the enzyme hydrolyzes NAD(+) to nicotinamide and transfers ADP ribose units to a variety of nuclear proteins, including histones and PARP-1 itself. This process is important in facilitating DNA repair. However, excessive activation of PARP-1 can lead to significant decrements in NAD(+), and ATP depletion, and cell death (suicide hypothesis). In response to cellular damage by oxygen radicals or excitotoxicity, a rapid and strong activation of PARP-1 occurs in neurons. Excessive PARP-1 activation is implicated in a variety of insults, including cerebral and cardiac ischemia, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism, traumatic spinal cord injury, and streptozotocin-induced diabetes. The use of PARP inhibitors has, therefore, been proposed as a protective therapy in decreasing excitotoxic neuronal cell death, as well as ischemic and other tissue damage. Excitotoxic brain lesions initially result in the primary destruction of brain parenchyma and subsequently in secondary damage of neighboring neurons hours after the insult. This secondary damage of initially surviving neurons accounts for most of the volume of the infarcted area and the loss of brain function after a stroke. One major component of secondary neuronal damage is the migration of macrophages and microglial cells toward the sites of injury, where they produce large quantities of toxic cytokines and oxygen radicals. Recent evidence indicates that this microglial migration is strongly controlled in living brain tissue by expression of the integrin CD11a, which is regulated in turn by PARP-1, proposing that PARP-1 downregulation may, therefore, be a promising strategy in protecting neurons from this secondary damage, as well. Studies demonstrating an important role for PARP-1 in the regulation of gene transcription have further increased the intricacy of poly(ADP-ribosyl)ation in the control of cell homeostasis and challenge the notion that energy collapse is the sole mechanism by which poly(ADP-ribose) formation contributes to cell death. The hypothesis that PARPs might regulate cell fate as essential modulators of death and survival transcriptional programs is discussed with relation to nuclear factor kappaB and p53.

There is differential loss of pyramidal cells from the human hippocampus with survival after blunt head injury

The experimental literature has shown that neurons within sub-fields of the hippocampus possess differential sensitivities to cell loss after different types of insult to the brain. In humans, after blunt head injury, differential neuronal responses between sub-fields of the hippocampus up to 72 hours after injury have been documented. But, in only a small part of the literature have data for alterations in real numbers of neurons been provided. In this study the hypothesis was tested that, after severe blunt head injury in humans, the total number of neurons within a defined volume of brain tissue differed between different sub-fields of the hippocampus and between groups of patients with differing post-traumatic survivals. Stereological methods were used to measure total cross-sectional area of sub-fields of the hippocampus taken at the level of the lateral geniculate nucleus and count numbers of neurons within each of the CA1, CA2, CA3, and CA4 sub-fields of the hippocampus in patients. The patients used in this study were categorized as follows: Group 1 (early) had survived for 1 week or less; Group 2 (late) survived 6 months or longer after fatal severe head injury; and Group 3 (controls) consisted of age-matched patients that had no history of head injury or disease prior to death. There was a significant loss in cross-sectional area in sub-fields CA3 and CA4 at 1 week or less after injury and in sub-field CA1 at 6 months and greater survival. There was no change in CA2. There was loss of neurons from within a predefined volume of brain tissue in sub-fields CA1, CA3, and CA4 one week or less after injury. But there was no loss in CA2. There was continued loss of neurons from sub-fields CA1 and CA4 between 1 week and 6 months and greater survival, but there was no loss of neurons in sub-fields CA2 and CA3 within the same period. These novel data show that after human severe head injury there is first an acute loss (1 week or less survival) of pyramidal neurons in all hippocampal sub-fields except CA2. Second, there is an ongoing loss of neurons in sub-field CA1 and, most notably, in sub-field CA4, in patients surviving for more than 6 months. However, in neither group of patients is there loss of neurons from sub-field CA2.

Reduced brain infarct volume and improved neurological outcome by inhibition of the NR2B subunit of NMDA receptors by using CP101,606-27 alone and in combination with rt-PA in a thromboembolic stroke model in rats

OBJECT

A novel postsynaptic antagonist of N-methyl-D-aspartate (NMDA) receptors, CP-101,606-27 may attenuate the effects of focal ischemia. In current experiments, the authors investigated its neuroprotective effect alone and in combination with recombinant tissue plasminogen activator (rt-PA) in thromboembolic focal cerebral ischemia in rats.

METHODS

Forty-eight male Wistar rats underwent embolization of the right middle cerebral artery to produce focal cerebral ischemia. After random division into six groups (eight rats in each group), animals received: vehicle; low-dose (LD) CP-101, 606-27, 14.4 mg/kg; high-dose (HD) CP- 101,606-27, 28.8 mg/kg; rt-PA, 10 mg/kg; low-dose combination (LDC) CP- 101,606-27, 14.4 mg/kg plus rt-PA, 10 mg/kg; or high-dose combination (HDC) CP- 101,606-27, 28.8 mg/kg plus rt-PA, 10 mg/kg) 2 hours after induction of embolic stroke. Animals were killed 48 hours after the onset of focal ischemia. Brain infarction volume, neurobehavioral outcome, poststroke seizure activity, poststroke mortality, and intracranial hemorrhage incidence were observed and evaluated. Compared with vehicle-treated animals (39.4 +/- 8.6%) 2 hours posttreatment with CP-101,606-27 or rt-PA or in combination a significant reduction in the percentage of brain infarct volume was seen (LD CP-101,606-27: 20.8 +/- 14.3%, p < 0.05; HD CP-101,606-27: 10.9 +/- 3.2%, p < 0.001; rt-PA: 21.1 +/- 7.3%, p < 0.05; LDC, 18.6 +/- 11.5%, p < 0.05; and HDC: 15.2 +/- 10.1%, p < 0.05; compared with control: 39.4 +/- 8.6%). Combination of CP-101,606-27 with rt-PA did not show a significantly enhanced neuroprotective effect. Except for the control and LDC treatment groups, neurobehavioral outcome was significantly improved 24 hours after embolic stroke in animals in all other active therapeutic groups receiving CP-101,606-27 or rt-PA or in combination. The authors also observed that treatment with HD CP-101,606-27 decreased poststroke seizure activity.

CONCLUSIONS

The data in this study suggested that postischemia treatment with CP-101,606-27 is neuroprotective in the current stroke model; however, the authors also note that although rt-PA may offer modest protection when used alone, combination with CP-101,606-27 did not appear to enhance its effects.

Strategies for regeneration and repair in spinal cord traumatic injury

Spinal cord injury is frequently followed by the loss of supraspinal control of sensory, autonomic and motor functions at the sublesional level. In order to enhance recovery in spinal cord-injured patients, we have developed three fundamental strategies in experimental models. These strategies define in turn three chronological levels of postlesional intervention in the spinal cord. Neuroprotection soon after injury using pharmacological tools to reduce the progressive secondary injury processes that follow during the first week after the initial lesion. This strategy was conducted up to clinical trials, showing that a pharmacological therapy can reduce the permanent neurological deficit that usually follows an acute injury of the central nervous system (CNS). A second strategy, which is initiated not long after the lesion, aims at promoting axonal regeneration by acting on the main barrier to regeneration of lesioned axons: the glial scar. Finally a mid-term substitutive strategy is the management of the sublesional spinal cord by sensorimotor stimulation and/or supply of missing key afferents, such as monoaminergic systems. These three strategies are reviewed. Only a combination of these different approaches will be able to provide an optimal basis for potential therapeutic interventions directed to functional recovery after spinal cord injury.

Neuroprotective effect of memantine in different retinal injury models in rats

PURPOSE

To evaluate the neuroprotective effect of memantine, an NMDA receptor channel blocker, in two retinal ganglion cell (RGC) injury models in rats.

METHODS

Neuroprotective effect of memantine was tested in partial optic nerve injury and chronic ocular hypertensive models. In the optic nerve injury model, memantine (0.1 - 30 mg/kg) was injected intraperitoneally immediately after injury. Two weeks later, optic nerve function was determined by measuring compound action potential and surviving RGC was determined by retrograde labeling with dextran tetramethyl rhodamine. Chronic ocular hypertension was attained by laser photocoagulation of episcleral and limbal veins. Memantine (5 or 10 mg/kg) was administered continuously each day with an osmotic pump, either immediately after or 10 days after first laser photocoagulation, for 3 weeks, after which RGC survival was determined.

RESULTS

Two weeks after partial optic nerve injury, there was approximately 80% reduction in RGC number. Memantine (5 mg/kg) caused a twofold increase in compound action potential amplitude and a 1.7-fold increase in survival of RGCs, respectively. In the chronic ocular hypertension model there was 37% decrease in RGCs after 3 weeks of elevated intraocular pressure. Memantine (10 mg/kg daily) reduced ganglion cell loss to 12% when applied immediately after first laser photocoagulation, and prevented any further loss when applied 10 days after first laser photocoagulation.

CONCLUSION

The protective effect of memantine suggests that excessive stimulation of NMDA receptors by glutamate is involved in causing cell damage in these RGC injury models.

Neuroprotection by T-cells depends on their subtype and activation state

This study analyzes how the antigen specificity, the subtype, and the activation state of T cells modulate their recently discovered neuroprotective potential. We assessed the prevention from neuronal damage in organotypic entorhinal-hippocampal slice cultures after co-culture with Th1 and Th2 cells either specific for myelin basic protein (MBP) or ovalbumin (OVA). We found that MBP-specific Th2 cells were the most effective in preventing central nervous system (CNS) tissue from secondary injury. This neuroprotective T cell effect appears to be mediated by soluble factors. After stimulation with phorbol myristate acetate and ionomycin, all T cells were most effective in preventing neuronal death. Our data show that the T cell subtype and activation state are important features in determining the neuroprotective potential of these cells.

Ferritin induction protects cortical astrocytes from heme-mediated oxidative injury

Hemin is released from hemoglobin after CNS hemorrhage and may contribute to its cytotoxic effect. In a prior study, we demonstrated that heme oxygenase-1 induction protected murine cortical astrocytes from hemoglobin toxicity. Since heme metabolism releases iron, this observation suggested that these cells are able to effectively sequester and detoxify free iron. In this study, we tested the hypotheses that astrocytes increased ferritin synthesis after exposure to heme-bound iron, and that this induction protected cells from subsequent exposure to toxic concentrations of hemin. Incubation with low micromolar concentrations of hemin, hemoglobin, or ferrous sulfate increased ferritin expression, as detected on immunoblots stained with a polyclonal antibody that was raised against horse spleen ferritin. Time course studies demonstrated an increase in ferritin levels within 2 h. Weak and scattered cellular staining was detected by immunohistochemistry in control, untreated cultures, while diffuse immunoreactivity was observed in cultures exposed to heme-bound iron. An enhanced ferritin band was detected on immunoblots from cultures that were treated with purified apoferritin, consistent with astrocytic ferritin uptake. Immunoreactivity after apoferritin treatment was not altered by concomitant treatment with cycloheximide. Pretreatment with apoferritin protected astrocytes from hemin toxicity in a concentration-dependent fashion between 1 and 4 mg/ml. At the highest concentration, cell death due to a 6-h exposure to 30 microM hemin was decreased by about 85%. A protective effect was also produced by induction of endogenous ferritin with nontoxic concentrations of ferrous sulfate, hemoglobin, or hemin. These results suggest that cortical astrocytes respond to exogenous heme-bound or free iron by rapidly increasing ferritin synthesis. The combined action of heme oxygenase-1 and ferritin may be a primary astrocytic defense against heme-mediated injury.

The tissue-specific self-pathogen is the protective self-antigen: the case of uveitis

Vaccination with peptides derived from interphotoreceptor retinoid-binding protein (a self-Ag that can cause experimental autoimmune uveoretinitis) resulted in protection of retinal ganglion cells from glutamate-induced death or death as a consequence of optic nerve injury. In the case of glutamate insult, no such protection was obtained by vaccination with myelin Ags (self-Ags associated with an autoimmune disease in the brain and spinal cord that evokes a protective immune response against consequences of injury to myelinated axons). We suggest that protective autoimmunity is the body's defense mechanism against destructive self-compounds, and an autoimmune disease is the outcome of a failure to properly control such a response. Accordingly, the specific self-Ag (although not necessarily its particular epitopes) used by the body for protection against potentially harmful self-compounds (e.g., glutamate) can be inferred from the specificity of the autoimmune disease associated with the site at which the stress occurs (irrespectively of the type of stress) and is in need of help.

Relationship between NOC/oFQ, dynorphin, and COX-2 activation in impaired NMDA cerebrovasodilation after brain injury

Previous studies have observed that the recently described endogenous opioid, nociceptin/orphanin FQ (NOC/oFQ), contributes to impairment of N-methyl-D-aspartate (NMDA)-induced cerebrovasodilation following fluid percussion brain injury (FPI) via a cyclooxygenase (COX)-dependent generation of superoxide anion (O(2)(-)). This study was designed to investigate the relationship between NOC/oFQ, another opioid, dynorphin, and activation of the COX-2 isoform of the enzyme in such impaired dilation to NMDA after FPI in piglets equipped with a closed cranial window. Superoxide dismutase (SOD)-inhibitable nitroblue tetrazolium (NBT) reduction was determined as an index of O(-)(2) generation. Under non-brain injury conditions, NOC/oFQ (10(-10) M), the CSF concentration observed after FPI, increased CSF dynorphin, while the NOC/oFQ antagonist [F/G] NOC/oFQ (1-13) NH(2) attenuated the stimulated release of dynorphin following FPI (34 +/- 3 and 97 +/- 6 vs. 36 +/- 3 and 68 +/- 8 pg/mol for CSF dynorphin before and after FPI in untreated and NOC/oFQ antagonist-pretreated animals). FPI increased SOD-inhibitable NBT reduction, but pretreatment with norbinaltorphimine, a dynorphin antagonist, or NS398, a COX-2 inhibitor, blunted such reduction (1 +/- 1 vs. 19 +/- 3 vs. 4 +/- 1 vs. 4 +/- 1 pmol/mm(2) for control, FPI, FPI-norbinaltorphimine and FPI-NS398, respectively). Under non-brain injury conditions, dynorphin, in a concentration observed in CSF after FPI, also increased SOD-inhibitable NBT reduction, which was blunted by NS398. NMDA-induced pial artery dilation was reversed to vasoconstriction following FPI, but pretreatment with norbinaltorphimine or NS398 partially protected such responses (9 +/- 1 and 16 +/- 1, control; - 8 +/- 1 and - 13 +/- 2, FPI; 6 +/- 1 and 12 +/- 1% FPI-norbinaltorphimine for NMDA 10(-8), 10(-6) M, respectively). These data show that NOC/oFQ modulates the CSF release of dynorphin after FPI. These data also show that dynorphin contributes to O(2)(-) generation after FPI via COX-2 activation. These data additionally indicate that dynorphin and COX-2 activation contribute to impairment of NMDA pial artery dilation after FPI. Finally, these data suggest that NOC/oFQ impairs NMDA dilation postinsult via the sequential release of dynorphin, activation of COX-2, and generation of O(2)(-).

Attenuation of the electrophysiological function of the corpus callosum after fluid percussion injury in the rat

This study describes a new method used to evaluate axonal physiological dysfunction following fluid percussion induced traumatic brain injury (TBI) that may facilitate the study of the mechanisms and novel therapeutic strategies of posttraumatic diffuse axonal injury (DAI). Stimulated compound action potentials (CAP) were recorded extracellularly in the corpus callosum of superfused brain slices at 3 h, and 1, 3, and 7 days following central fluid percussion injury and demonstrated a temporal pattern of functional deterioration. The maximal CAP amplitude (CAPA) covaried with the intensity of impact 1 day following sham, mild (1.0-1.2 atm), and moderate (1.8-2.0 atm) injury (p < 0.05; 1.11 +/- 0.10, 0.82 +/- 0.11, and 0.49 +/- 0.08 mV, respectively). The CAPA in sham animals were approximately 1.1 mV and did not vary with survival interval (3 h, and 1, 3, and 7 days); however, they were significantly decreased at each time point following moderate injury (p < 0.05; 0.51 +/- 0.11, 0.49 +/- 0.08, 0.46 +/- 0.10, and 0.75 +/- 0.13 mV, respectively). The CAPA at 7 days in the injured group were higher than at 3 h, and 1 and 3 days. H&E and amyloid precursor protein (APP) light microscopic analysis confirmed previously reported trauma-induced axonal injury in the corpus callosum seen after fluid percussion injury. Increased APP expression was confirmed using Western blotting showing significant accumulation at 1 day (IOD 913.0 +/- 252.7; n = 3; p = 0.05), 3 days (IOD 753.1 +/- 159.1; n = 3; p = 0.03), and at 7 days (IOD 1093.8 = 105.0; n = 3; p = 0.001) compared to shams (IOD 217.6 +/- 20.4; n = 3). Thus, we report the characterization of white matter axonal dysfunction in the corpus callosum following TBI. This novel method was easily applied, and the results were consistent and reproducible. The electrophysiological changes were sensitive to the early effects of impact intensity, as well as to delayed changes occurring several days following injury. They also indicated a greater degree of attenuation than predicted by APP expression changes alone.

A mouse model of acute ischemic spinal cord injury

Mice models of spinal cord injury (SCI) should improve our knowledge of the mechanisms of injury and repair of the nervous tissue. They represent a powerful tool for the development of therapeutic strategies in the fields of pharmacological, cellular, and genetic approaches of neurotrauma. We demonstrate here that the photochemical graded ischemic spinal cord injury model, described in rats, can be successfully adapted in mice, in a reliable and reproducible manner. Following the intravenous injection of Rose Bengal, the translucent dorsal surface of the T9 vertebral laminae of C57BL/6 female mice was irradiated with a 560-nm wavelength-light (3-8 min depending on the experimental group). Animals were sacrificed at 1 day or 7 days after injury. Functional tests were performed daily for motor, sensory, autonomic, and reflex responses. Lesion histopathology was assessed for lesion length, percentage of residual white matter, and astrocytic reactivity. Experimental groups demonstrated a functional deficit, which was correlated to the increase of the irradiation time and, therefore, to the severity of the injury. Histopathological and immunocytochemical data were reliable morphological measurements characterizing the degree of injury, which were strongly correlated to the severity of the functional impairment. Despite differences in the mechanism of injury, the wound healing response described in other traumatic SCI mice models was confirmed (no cavitation and, conversely, the formation of a dense connective tissue matrix). In this context, the precise understanding of the mechanisms of healing response after SCI in mice and of neurochemical kinetics appear to be crucial in the development of therapeutic strategies of CNS repair. Thus, the possible use of an increasing collection of transgenic mice offers a new dimension for experimental research in this area. The ischemic photochemical model of SCI in mice represents a relevant model that can play a key role in this new era of neurotrauma research.

Traumatic subarachnoid hemorrhage: demographic and clinical study of 750 patients from the European brain injury consortium survey of head injuries

OBJECTIVE

Previous reports identified the presence of traumatic subarachnoid hemorrhage (tSAH) on admission computed tomographic (CT) scans as an independent prognostic factor in worsening outcomes. The mechanism underlying the link between tSAH and prognosis has not been clarified. The aim of this study was to investigate the association between CT evidence of tSAH and outcomes after moderate or severe head injuries.

METHODS

In a survey organized by the European Brain Injury Consortium, data on initial severity, treatment, and subsequent outcomes were prospectively collected for 1005 patients with moderate or severe head injuries who were admitted to one of the 67 European neurosurgical units during a 3-month period in 1995. The CT findings were classified according to the Traumatic Coma Data Bank classification system, and the presence or absence of tSAH was recorded separately in the initial CT scan forms.

RESULTS

Complete data on early clinical features, CT findings, and outcomes at 6 months were available for 750 patients, of whom 41% exhibited evidence of tSAH on admission CT scans. There was a strong, highly statistically significant association between the presence of tSAH and poor outcomes. In fact, 41% of patients without tSAH achieved the level of good recovery, whereas only 15% of patients with tSAH achieved this outcome. Patients with tSAH were significantly older (median age, 43 yr; standard deviation, 21.1 yr) than those without tSAH (median age, 32 yr; standard deviation, 19.5 yr), and there was a significant tendency for patients with tSAH to exhibit lower Glasgow Coma Scale scores at the time of admission. A logistic regression analysis of favorable/unfavorable outcomes demonstrated that there was still a very strong association between tSAH and outcomes after simultaneous adjustment for age, Glasgow Coma Scale Motor Scores, and admission CT findings (odds ratio, 2.49; 95% confidence interval, 1.74-3.55; P < 0.001). Comparison of the time courses for 164 patients with early (within 14 d after injury) deaths demonstrated very similar patterns, with an early peak and a subsequent decline; there was no evidence of a delayed increase in mortality rates for either group of patients (with or without tSAH).

CONCLUSION

These findings for an unselected series of patients confirm previous reports of the adverse prognostic significance of tSAH. The data support the view that death among patients with tSAH is related to the severity of the initial mechanical damage, rather than to the effects of delayed vasospasm and secondary ischemic brain damage.

Traumatic intracerebellar hemorrhage: clinicoradiological analysis of 81 patients

OBJECTIVE

We report 81 patients with a traumatic intracerebellar hemorrhagic contusion or hematoma managed between 1996 and 1998 at 13 Italian neurosurgical centers.

METHODS

Each center provided data about patients' clinicoradiological findings, management, and outcomes, which were retrospectively reviewed.

RESULTS

A poor result occurred in 36 patients (44.4%). Forty-five patients (55.6%) had favorable results. For the purpose of data analysis, patients were divided into two groups according to their admission Glasgow Coma Scale (GCS) scores. In Group 1 (39/81 cases; GCS score, > or =8), the outcome was favorable in 95% of cases. In Group 2 (42/81 cases; GCS score, <8), the outcome was poor in 81% of cases. Twenty-seven patients underwent posterior fossa surgery. Factors correlating with outcome were GCS score, status of the basal cisterns and the fourth ventricle, associated supratentorial traumatic lesions, mechanism of injury, and intracerebellar clot size. Multivariate analysis showed significant independent prognostic effect only for GCS score (P = 0.000) and the concomitant presence of supratentorial lesions (P = 0.0035).

CONCLUSION

This study describes clinicoradiological findings and prognostic factors regarding traumatic cerebellar injury. A general consensus emerged from this analysis that a conservative approach can be considered a viable, safe treatment option for noncomatose patients with intracerebellar clots measuring less than or equal to 3 cm, except when associated with other extradural or subdural posterior fossa focal lesions. Also, a general consensus was reached that surgery should be recommended for all patients with clots larger than 3 cm. The pathogenesis, biomechanics, and optimal management criteria of these rare lesions are still unclear, and larger observational studies are necessary.

Postischemic intravenous administration of magnesium sulfate inhibits hippocampal CA1 neuronal death after transient global ischemia in rats

OBJECTIVE

We aimed to determine an effective dose schedule for intravenously administered magnesium, to establish its neuroprotective efficacy in both pre- and postischemic treatment paradigms, and to compare the neuroprotective properties of MgSO(4) and MgCl(2).

METHODS

Rats that had been subjected to the bilateral carotid artery occlusion plus hypotension model of transient forebrain cerebral ischemia received either an intravenously administered loading dose (LD) of 360 micromol/kg MgSO(4) only or an intravenously administered LD of 360 micromol/kg followed by a 48-hour intravenous infusion of MgSO(4) at either 60, 120, 240, or 480 micromol/kg/h. For evaluation of the efficacy of MgSO(4) after ischemia, the dose (LD, 360 micromol/kg; infusion, 120 micromol/kg/h) that provided maximal neuroprotection before ischemia was administered 4, 8, 12, or 24 hours after ischemia. MgCl(2) (LD, 360 micromol/kg; infusion, 120 micromol/kg/h) was administered before and 8 hours after ischemia. At 7 days after ischemia, hippocampal CA1 neurons were histologically examined for protection.

RESULTS

Animals that received the LD only demonstrated 33% hippocampal CA1 neuronal survival. Animals that received the LD followed by continuous infusion of MgSO(4) at either 60, 120, 240, or 480 micromol/kg/h demonstrated 30, 80, 16, and less than 5% CA1 neuronal survival, respectively. MgSO(4) treatment commencing at 4, 8, 12, or 24 hours resulted in 82, 71, 52, and 33% CA1 neuronal survival, respectively. Preischemic and 8-hour postischemic administration of MgCl(2) resulted in 50% and less than 5% CA1 neuronal survival, respectively.

CONCLUSION

These results demonstrate a neuroprotective intravenous dose of MgSO(4), which is effective when administered before or late after ischemia, and a previously uncharacterized dose-response curve for MgSO(4).

Harnessing the immune system for neuroprotection: therapeutic vaccines for acute and chronic neurodegenerative disorders

Nerve injury causes degeneration of directly injured neurons and the damage spreads to neighboring neurons. Research on containing the damage has been mainly pharmacological, and has not recruited the immune system. We recently discovered that after traumatic injury to the central nervous system (spinal cord or optic nerve), the immune system apparently recognizes certain injury-associated self-compounds as potentially destructive and comes to the rescue with a protective antiself response mediated by a T-cell subpopulation that can recognize self-antigens. We further showed that individuals differ in their ability to manifest this protective autoimmunity, which is correlated with their ability to resist the development of autoimmune diseases. This finding led us to suggest that the antiself response must be tightly regulated to be expressed in a beneficial rather than a destructive way. In seeking to develop a neuroprotective therapy by boosting the beneficial autoimmune response to injury-associated self-antigens, we looked for an antigen that would not induce an autoimmune disease. Candidate vaccines were the safe synthetic copolymer Cop-1, known to cross-react with self-antigens, or altered myelin-derived peptides. Using these compounds as vaccines, we could safely boost the protective autoimmune response in animal models of acute and chronic insults of mechanical or biochemical origin. Since this vaccination is effective even when given after the insult, and because it protects against the toxicity of glutamate (the most common mediator of secondary degeneration), it can be used to treat chronic neurodegenerative disorders such as glaucoma, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis.

Protective autoimmunity as a T-cell response to central nervous system trauma: prospects for therapeutic vaccines

Immune activity in general, and autoimmunity in particular, have long been considered as harmful in the context of central nervous system (CNS) trauma. Increasing evidence suggests, however, that the injured CNS can benefit from autoimmune manipulations. Active or passive immunization with CNS-associated self antigens was shown to promote recovery from a CNS insult. It is now also evident that this beneficial 'autoimmunity' is not solely an outcome of immune manipulation but is also a physiological response, evoked by a non-pathogenic insult and apparently designed to counteract the insult-related toxicity which is induced in part by essential physiological compounds present in excess of their normal levels. It appears that when the buffering capacity of constitutive local mechanisms (transporters, enzymes, etc.) that normally regulate these compounds is exceeded, assistance is recruited from the immune system. Like the overactive physiological compounds themselves, the immune system needs to be rigorously regulated in order to produce adequate phagocytic activity and the required quantity of cytokines and growth factors at the right time and place. Boosting of this autoimmune response is potentially a powerful strategy for neuroprotective therapy.

An overview of new and novel pharmacotherapies for use in traumatic brain injury

1. Although a number of interventional pharmacotherapies have undergone clinical trial in traumatic brain injury (TBI), none has shown considerable promise. The present short review will examine some of the more novel compounds that have been proposed recently as potential therapeutic agents for use in TBI. 2. Previous experimental studies have demonstrated that brain intracellular free magnesium significantly declines following TBI and that the administration of magnesium salts attenuates the post-traumatic neurological deficits. More recent studies have established that magnesium salts administered after trauma enter the brain intracellular space and reduce the size of the lesion volume. Such protection could be afforded through attenuation of both necrotic and apoptotic cell death. Magnesium salts are currently on clinical trial in TBI. 3. Cyclosporine A is known to inhibit opening of the mitochondrial permeability transition pore. Administration of cyclosporine A after TBI has been shown to attenuate axonal injury and decrease the resultant lesion volume. Therefore, inhibitors of mitochondrial transition pore opening and resultant attenuation of apoptosis show some promise as neuroprotective agents. 4. Recent evidence has shown that substance P antagonists may decrease lesion volume and improve neurological outcome after ischaemia. Similar findings have recently been reported in TBI. The fact that substance P antagonists are known to reduce neurogenic inflammation, oedema formation and are clinically being trialed as both antidepressants and antinociceptive agents suggests that these agents warrant further investigation as therapeutic agents following TBI. 5. There are numerous contradictions in the literature regarding the potential neuroprotective effects of the hormones oestrogen and progesterone. Recent studies suggest that both hormones are protective in TBI and further studies are required to ascertain the mechanisms associated with this protection and any potential for clinical application.

Increased post-traumatic survival of neurons in IL-6-knockout mice on a background of EAE susceptibility

Axonal injury initiates a process of neuronal degeneration, with resulting death of neuronal cell bodies. We show here that in C57BL/6J mice, previously shown to have a limited ability to manifest a post-traumatic protective immunity, the rate of neuronal survival is increased if IL-6 is deficient during the first 24 hours after optic nerve injury. Immunocytochemical staining preformed 7 days after the injury revealed an increased number of activated microglia in the IL-6-deficient mice compared to the wild-type mice. In addition, IL-6-deficient mice showed an increased resistance to glutamate toxicity. These findings suggest that the presence of IL-6 during the early post-traumatic phase, at least in mice that are susceptible to autoimmune disease development, has a negative effect on neuronal survival. This further substantiates the contention that whether immune-derived factors are beneficial or harmful for nerve recovery after injury depends on the phenotype of the immune cells and the timing and nature of their dialog with the damaged neural tissue.

Gacyclidine: a new neuroprotective agent acting at the N-methyl-D-aspartate receptor

Gacyclidine is a new phencyclidine derivative with neuroprotective properties. Tritiated gacyclidine and its enantiomers bind to NMDA receptors with binding parameters similar to those of other non-competitive NMDA receptor antagonists. The (-)enantiomer, (-)GK11, exhibits an affinity (2.5 nM) similar to that of dizocilpine (MK-801), while the (+)enantiomer, (+)GK11, has a 10 times lower affinity. When its interaction with NMDA receptors is prevented, gacyclidine binds also to "non-NMDA" binding sites which are mainly located in the molecular layer of the cerebellum on the dendritic tree of Purkinje cells. These binding sites do not appear to be related to any known neurotransmitters. In primary cortical cultures, gacyclidine and its enantiomers, at 0.1 to 5.0 microM, prevent glutamate-induced neuronal death. In rats, in vivo neurotoxicity of gacyclidine is far low than that of MK-801. No necrotic neurons were detected in animals sacrificed at 18 or 96 h after treatment with gacyclidine (1, 5, 10 or 20 mg/kg i.v.). At the highest (20 mg/kg) but not the lower doses (1-100 mg/kg) electron microscopy revealed the presence of few cytoplasmic or intramitochondrial vacuoles. In soman-treated monkeys gacyclidine enhanced neuroprotective activity of "three drugs cocktail" (atropine + diazepam + pralidoxime). Moreover, in rats, gacyclidine exerts a dose- and time-dependent neuroprotection in three models of spinal cord lesion. Beneficial effects of gacyclidine include reduction of lesion size and improvement of functional parameters after injury. In traumatic brain injury models gacyclidine improves also behavioral parameters and neuronal survival. Optimal protection is obtained when gacyclidine is administered at 0 to 30 min after injury. It is, therefore, concluded that gacyclidine exhibits neuroprotective effects similar to those of other NMDA receptor antagonists, with the advantage of being substantially less neurotoxic maybe due to its interaction with "non-NMDA" binding sites.

Glutamate uptake

Brain tissue has a remarkable ability to accumulate glutamate. This ability is due to glutamate transporter proteins present in the plasma membranes of both glial cells and neurons. The transporter proteins represent the only (significant) mechanism for removal of glutamate from the extracellular fluid and their importance for the long-term maintenance of low and non-toxic concentrations of glutamate is now well documented. In addition to this simple, but essential glutamate removal role, the glutamate transporters appear to have more sophisticated functions in the modulation of neurotransmission. They may modify the time course of synaptic events, the extent and pattern of activation and desensitization of receptors outside the synaptic cleft and at neighboring synapses (intersynaptic cross-talk). Further, the glutamate transporters provide glutamate for synthesis of e.g. GABA, glutathione and protein, and for energy production. They also play roles in peripheral organs and tissues (e.g. bone, heart, intestine, kidneys, pancreas and placenta). Glutamate uptake appears to be modulated on virtually all possible levels, i.e. DNA transcription, mRNA splicing and degradation, protein synthesis and targeting, and actual amino acid transport activity and associated ion channel activities. A variety of soluble compounds (e.g. glutamate, cytokines and growth factors) influence glutamate transporter expression and activities. Neither the normal functioning of glutamatergic synapses nor the pathogenesis of major neurological diseases (e.g. cerebral ischemia, hypoglycemia, amyotrophic lateral sclerosis, Alzheimer's disease, traumatic brain injury, epilepsy and schizophrenia) as well as non-neurological diseases (e.g. osteoporosis) can be properly understood unless more is learned about these transporter proteins. Like glutamate itself, glutamate transporters are somehow involved in almost all aspects of normal and abnormal brain activity.

Neuronal survival after CNS insult is determined by a genetically encoded autoimmune response

Injury to the CNS is often followed by a spread of damage (secondary degeneration), resulting in neuronal losses that are substantially greater than might have been predicted from the severity of the primary insult. Studies in our laboratory have shown that injured CNS neurons can benefit from active or passive immunization with CNS myelin-associated antigens. The fact that autoimmune T-cells can be both beneficial and destructive, taken together with the established phenomenon of genetic predisposition to autoimmune diseases, raises the question: will genetic predisposition to autoimmune diseases affect the outcome of traumatic insult to the CNS? Here we show that the survival rate of retinal ganglion cells in adult mice or rats after crush injury of the optic nerve or intravitreal injection of a toxic dosage of glutamate is up to twofold higher in strains that are resistant to the CNS autoimmune disease experimental autoimmune encephalomyelitis (EAE) than in susceptible strains. The difference was found to be attributed, at least in part, to a beneficial T-cell response that was spontaneously evoked after CNS insult in the resistant but not in the susceptible strains. In animals of EAE-resistant but not of EAE-susceptible strains devoid of mature T-cells (as a result of having undergone thymectomy at birth), the numbers of surviving neurons after optic nerve injury were significantly lower (by 60%) than in the corresponding normal animals. Moreover, the rate of retinal ganglion cell survival was higher when the optic nerve injury was preceded by an unrelated CNS (spinal cord) injury in the resistant strains but not in the susceptible strains. It thus seems that, in normal animals of EAE-resistant strains (but not of susceptible strains), the injury evokes an endogenous protective response that is T-cell dependent. These findings imply that a protective T-cell-dependent response and resistance to autoimmune disease are regulated by a common mechanism. The results of this study compel us to modify our understanding of autoimmunity and autoimmune diseases, as well as the role of autoimmunity in non-autoimmune CNS disorders. They also obviously have far-reaching clinical implications in terms of prognosis and individual therapy.

New treatments for concussion: the next millennium beckons

As increased understanding of the pathophysiology of mild traumatic brain injury and concussion develops, so the scientific rationale for interventional pharmacological therapy becomes paramount. A number of agents have been postulated or have been the subject of anecdotal noncontrolled trials. This paper reviews the published evidence in this regard. To date no effective pharmacological therapy exists that satisfies Class I evidence-based medicine criteria.

Detection of single- and double-strand DNA breaks after traumatic brain injury in rats: comparison of in situ labeling techniques using DNA polymerase I, the Klenow fragment of DNA polymerase I, and terminal deoxynucleotidyl transferase

DNA damage is a common sequela of traumatic brain injury (TBI). Available techniques for the in situ identification of DNA damage include DNA polymerase I-mediated biotin-dATP nick-translation (PANT), the Klenow fragment of DNA polymerase I-mediated biotin-dATP nick-end labeling (Klenow), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). While TUNEL has been widely utilized to detect primarily double-strand DNA breaks, the use of PANT to detect primarily single-strand DNA breaks and Klenow to detect both single- and double-strand DNA breaks has not been reported after TBI. Accordingly, coronal brain sections from naive rats and rats at 0, 0.5, 1, 2, 6, 24, and 72 h (n = 3-5/group) after controlled cortical impact with imposed secondary insult were processed using the PANT, Klenow, and TUNEL methods. Cells with DNA breaks were detected by PANT in the ipsilateral hemisphere as early as 0.5 h after injury and were maximal at 6 h (cortex = 66.3+/-15.8, dentate gyrus 58.6+/-12.8, CA1 = 15.8+/-5.9, CA3 = 12.8+/-4.2 cells/x 400 field, mean +/- SEM, all p < 0.05 versus naive). Cells with DNA breaks were detected by Klenow as early as 30 min and were maximal at 24 h (cortex = 56.3+/-14.3, dentate gyrus 78.0+/-16.7, CA1 = 25.8+/-4.7, CA3 = 29.3+/-15.1 cells/x 400 field, all p < 0.05 versus naive). Cells with DNA breaks were not detected by TUNEL until 2 h and were maximal at 24 h (cortex = 47.7+/-21.4, dentate gyrus 63.0+/-11.9, CA1 = 5.6+/-5.4, CA3 = 6.9+/-3.7 cells/x 400 field, cortex and dentate gyrus p < 0.05 versus naive). Dual-label immunofluorescence revealed that PANT-positive cells were predominately neurons. These data demonstrate that TBI results in extensive DNA damage, which includes both single- and double-strand breaks in injured cortex and hippocampus. The presence of multiple types of DNA breaks implicate several pathways in the evolution of DNA damage after TBI.

Age-Dependent vasopressinergic modulation of Noc/oFQ-induced impairment of NMDA cerebrovasodilation after brain injury

This study was designed to characterize the role of vasopressin in nociceptin/orphanin FQ (NOC/oFQ)-induced impairment of NMDA cerebrovasodilation after fluid percussion brain injury (FPI) as a function of age in newborn (1-5 days old) and juvenile (3-4 weeks old) pigs equipped with a closed cranial window. Previous studies have observed that NOC/oFQ is released into CSF and contributes to impaired NMDA induced pial artery dilation following FPI to a greater extent in newborn versus juvenile pigs. Topical vasopressin (40 pg/mL), a concentration approximating that observed in CSF following FPI in the newborn, increased CSF NOC/oFQ from 69 +/- 3 to 102 +/- 8 pg/mol under non-FPI conditions. CSF NOC/oFQ was elevated within 60 min of FPI (70 +/- 3 to 444 +/- 51 pg/mL), but release was attenuated by MEAVP, a vasopressin antagonist, in the newborn (71 +/- 3 to 146 +/- 11 pg/mL). CSF vasopressin and NOC/oFQ were not elevated as greatly in the juvenile following FPI and MEAVP correspondingly did not attenuate CSF NOC/oFQ release as much as in the newborn. Under noninjury conditions, vasopressin (40 pg/mL) coadministered with NMDA (10(-8), 10(-6) M) attenuated pial dilation to this excitatory amino acid (9 +/- 1% and 16 +/- 1% vs. 3 +/- 1% and 5 +/- 2%). Following FPI in the newborn, NMDA-induced pial artery dilation was reversed to vasoconstriction, and both NOC/oFQ and vasopressin receptor antagonists partially prevented these alterations (9 +/- 1%) and 16 +/- 1%, sham control; -7 +/- 1% and -12 +/- 1%, FPI; -2 +/- 1% and -3 +/- 1%, FPI-NOC/oFQ antagonist; and 1 +/- 1% and 4 +/- 1%, FPI-vasopressin antagonist). NMDA-induced pial dilation was only attenuated following FPI in the juvenile and modestly restored by NOC/oFQ and vasopressin receptor antagonists. These data show that vasopressin, in concentrations present in CSF following FPI, contributes to the release of CSF NOC/oFQ following such an insult. The greater release of vasopressin following FPI in the newborn contributes to the corresponding greater release of NOC/oFQ in the newborn versus the juvenile. Moreover, vasopressin also contributes to the impairment of NMDA cerebrovasodilation after brain injury to a greater extent in newborn versus juveniles. These data suggest that vasopressin modulates NOC/oFQ-induced impairment of NMDA cerebrovasodilation after brain injury in an age-dependent manner.

Physiological Approaches to Neuroprotection

In glaucoma, as in other degenerative diseases of the central nervous system (CNS), there are some neurons which, although susceptible to degeneration, are amenable to neuroprotection. Until very recently, attempts to attenuate the spread of damage after CNS trauma or in neurodegenerative diseases did not include recruitment of the immune system, because it was assumed that in the CNS any immune activity, particularly autoimmune activity, would be harmful. Using the injured optic nerve of the rat as a model, we recently showed, however, that this 'secondary degeneration' can be slowed down by a well-controlled adaptive immune response, which is mediated by T cells against CNS self-antigens, such as myelin basic protein (MBP), and can be achieved either by passive transfer of MBP-activated T cells or by active immunization with MBP. Accordingly, we suggested that autoimmune T cells can be neuroprotective. We further showed that the neuroprotective autoimmunity is a physiological response to the injury, perhaps insufficient in its natural state, but amenable to boosting. The neuroprotective activity of these T cells probably depends on their reactivation by their specific antigen after they are targeted to the injured nerve. As nerve degeneration is initiated and sustained by many factors, it would probably best be counteracted by a comprehensive type of therapy rather than treatment that addresses only some aspects of nerve damage. T cell therapy, being physiological rather than pharmaceutical in nature, may provide a global answer. However, since the neuroprotective immune response is directed against the self, it must be rigorously regulated to avoid inducing an autoimmune disease. We showed that the synthetic copolymer Cop-1 can passively or actively evoke T cell-mediated neuroprotection, probably by cross-reacting with MBP. Safe synthetic peptides that resemble self-antigens and are cross-activated by CNS-associated self antigens may be a useful starting point for the development of anti-self immunity for neuroprotective purposes.

Diminution of metabolism/blood flow uncoupling following traumatic brain injury in rats in response to high-dose human albumin treatment

OBJECT

The authors have recently demonstrated that high-dose human albumin is markedly neuroprotective in experimental traumatic brain injury (TBI) and cerebral ischemia. The pathophysiology of TBI involves acute uncoupling of cerebral glucose utilization and blood flow. The intent of this study was to establish whether the use of human albumin therapy in a model of acute TBI would influence this phenomenon.

METHODS

Anesthetized, physiologically regulated rats received moderate (1.5-2 atm) fluid-percussion injury to the parietal lobe. Fifteen minutes after trauma or sham injury, rats in one group received human albumin (2.5 g/kg) administered intravenously and those in another group received 0.9% saline vehicle. At 60 minutes and 24 hours posttrauma, autoradiographic studies of local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu) were conducted, and the LCMRglu/LCBF ratio was determined. Sham-injured rats had normal levels of LCBF and LCMRglu, and no differences between vehicle- and albumin-treated rats were evident. Sixty minutes after TBI, LCBF was moderately reduced bilaterally in vehicle-treated rats, whereas in albumin-treated animals, the LCBF contralateral to the side of injury was generally normal. Despite acutely depressed LCBF, LCMRglu in vehicle-treated rats at 60 minutes was paradoxically normal bilaterally, and foci of elevated LCMRglu were noted in the ipsilateral hippocampus and thalamus. By contrast, in albumin-treated rats studied 60 minutes post-TBI, reduced LCMRglu values were measured in the ipsilateral caudoputamen and parietal cortex, whereas LCMRglu in other ipsilateral and contralateral sites did not differ from that measured in sham-injured animals. The metabolism/blood flow ratio was normal in sham-injured rats, but became markedly elevated in vehicle-treated rats 60 minutes post-TBI (on average, by threefold ipsilaterally and 2.1-fold contralaterally). By contrast, the mean metabolism/blood flow ratio in albumin-treated animals was elevated by only 1.6-fold ipsilaterally and was normal contralaterally. Twenty-four hours after TBI, LCBF contralateral to the side of injury had generally returned to normal levels in the albumin-treated group.

CONCLUSIONS

These results demonstrate that human albumin therapy benefits the posttraumatic brain by diminishing the pronounced metabolism > blood flow dissociation that would otherwise occur within the 1st hour after injury. Viewed together with our previous evidence of histological neuroprotection, these findings indicate that human albumin therapy may represent a desirable treatment modality for acute TBI.

Dose-response curve and optimal dosing regimen of cyclosporin A after traumatic brain injury in rats

Acute neuropathology following experimental traumatic brain injury results in the rapid necrosis of cortical tissue at the site of injury. This primary injury is exacerbated in the ensuing hours and days via the progression of secondary injury mechanism(s) leading to significant neurological dysfunction. Recent evidence from our laboratory demonstrates that the immunosuppressant cyclosporin A significantly ameliorates cortical damage following traumatic brain injury. The present study extends the previous findings utilizing a unilateral controlled cortical impact model of traumatic brain injury in order to establish a dose-response curve and optimal dosing regimen of cyclosporin A. Following injury to adult rats, cyclosporin A was administrated at various dosages and the therapy was initiated at different times post-injury. In addition to examining the effect of cyclosporin A on the acute disruption of the blood-brain barrier following controlled cortical impact, we also assessed the efficacy of cyclosporin A to reduce tissue damage utilizing the fluid percussion model of traumatic brain injury. The findings demonstrate that the neuroprotection afforded by cyclosporin A is dose-dependent and that a therapeutic window exists up to 24h post-injury. Furthermore, the optimal cyclosporin dosage and regimen markedly reduces disruption of the blood-brain barrier acutely following a cortical contusion injury, and similarly affords significant neuroprotection following fluid percussion injury. These findings clearly suggest that the mechanisms responsible for tissue necrosis following traumatic brain injury are amenable to pharmacological intervention.

Vaccination for neuroprotection in the mouse optic nerve: implications for optic neuropathies

T-cell autoimmunity to myelin basic protein was recently shown to be neuroprotective in injured rat optic nerves. In the present study, using the mouse optic nerve, we examined whether active immunization rather than passive transfer of T-cells can be beneficial in protecting retinal ganglion cells (RGCs) from post-traumatic death. Before severe crush injury of the optic nerve, SJL/J and C3H.SW mice were actively immunized with encephalitogenic or nonencephalitogenic peptides of proteolipid protein (PLP) or myelin oligodendrocyte glycoprotein (MOG), respectively. At different times after the injury, the numbers of surviving RGCs in both strains immunized with the nonencephalitogenic peptides pPLP 190-209 or pMOG 1-22 were significantly higher than in injured controls treated with the non-self-antigen ovalbumin or with a peptide derived from beta-amyloid, a non-myelin-associated protein. Immunization with the encephalitogenic myelin peptide pPLP 139-151 was beneficial only when the disease it induced, experimental autoimmune encephalomyelitis, was mild. The results of this study show that survival of RGCs after axonal injury can be enhanced by vaccination with an appropriate self-antigen. Furthermore, the use of nonencephalitogenic myelin peptides for immunization apparently allows neuroprotection without incurring the risk of an autoimmune disease. Application of these findings might lead to a promising new approach for treating optic neuropathies such as glaucoma.

Gacyclidine: a new neuroprotective agent acting at the N-methyl-D-aspartate receptor

Gacyclidine is a new phencyclidine derivative with neuroprotective properties. Tritiated gacyclidine and its enantiomers bind to NMDA receptors with binding parameters similar to those of other non-competitive NMDA receptor antagonists. The (-)enantiomer, (-)GK11, exhibits an affinity (2.5 nM) similar to that of dizocilpine (MK-801), while the (+)enantiomer, (+)GK11, has a 10 times lower affinity. When its interaction with NMDA receptors is prevented, gacyclidine binds also to "non-NMDA" binding sites which are mainly located in the molecular layer of the cerebellum on the dendritic tree of Purkinje cells. These binding sites do not appear to be related to any known neurotransmitters. In primary cortical cultures, gacyclidine and its enantiomers, at 0.1 to 5.0 microM, prevent glutamate-induced neuronal death. In rats, in vivo neurotoxicity of gacyclidine is far low than that of MK-801. No necrotic neurons were detected in animals sacrificed at 18 or 96 h after treatment with gacyclidine (1, 5, 10 or 20 mg/kg i.v.). At the highest (20 mg/kg) but not the lower doses (1-100 mg/kg) electron microscopy revealed the presence of few cytoplasmic or intramitochondrial vacuoles. In soman-treated monkeys gacyclidine enhanced neuroprotective activity of "three drugs cocktail" (atropine + diazepam + pralidoxime). Moreover, in rats, gacyclidine exerts a dose- and time-dependent neuroprotection in three models of spinal cord lesion. Beneficial effects of gacyclidine include reduction of lesion size and improvement of functional parameters after injury. In traumatic brain injury models gacyclidine improves also behavioral parameters and neuronal survival. Optimal protection is obtained when gacyclidine is administered at 0 to 30 min after injury. It is, therefore, concluded that gacyclidine exhibits neuroprotective effects similar to those of other NMDA receptor antagonists, with the advantage of being substantially less neurotoxic maybe due to its interaction with "non-NMDA" binding sites.

Regional changes in kynurenic acid, quinolinic acid, and glial fibrillary acidic protein concentrations in the fetal sheep brain after experimentally induced placental insufficiency

OBJECTIVE

This study was undertaken to examine the effects of chronic embolization of the umbilical circulation during late gestation on regional concentrations of quinolinic acid and kynurenic acid (neuroactive products of tryptophan catabolism) and of the astrocyte-associated glial fibrillary acidic protein in the fetal brain.

STUDY DESIGN

Pregnant ewes bearing fetuses with long-term catheter placement were treated daily with injections of either saline solution (n = 4; control group) or mucopolysaccharide microspheres (n = 5; embolized group) into the umbilical circulation through a femoral artery catheter between 120 and 140 days' gestation. The fetuses in the embolized group received sufficient microspheres each day to reduce and maintain the femoral arterial PO2 at < or =12 mm Hg. Autopsies were performed at 140 days' gestation to obtain the fetal brain for chemical analysis.

RESULTS

Umbilical embolization resulted in nonacidemic hypoxia and hypoglycemia at 140 days' gestation. Quinolinic acid concentrations in the embolized group were significantly increased in the medulla, pons, midbrain, hypothalamus, and hippocampus, whereas kynurenic acid concentrations in the embolized group were reduced in the hippocampus and hypothalamus. There were significant reductions in glial fibrillary acidic protein contents in the occipitoparietal cortex, hippocampus, and pons in the embolized group.

CONCLUSION

Placental compromise during late pregnancy had effects on kynurenine metabolism and astrocyte function in some regions of the fetal sheep brain. We suggest that these changes increase the vulnerability of the brain to asphyxial injury during late gestation and the perinatal period.

Isoflurane improves long-term neurologic outcome versus fentanyl after traumatic brain injury in rats

Despite routine use of fentanyl in patients after traumatic brain injury (TBI), it is unclear if it is the optimal sedative/analgesic agent. Isoflurane is commonly used in experimental TBI. We hypothesized that isoflurane would be neuroprotective versus fentanyl after TBI. Rats underwent controlled cortical impact (CCI) and received 4 h of N2O/O2 (2:1) and either fentanyl (10 microg/kg i.v. bolus, 50 microg/kg/h infusion) or isoflurane (1% by inhalation) with controlled ventilation. Shams underwent identical preparation, without CCI. Functional outcome (beam balance, beam walking, Morris water maze [MWM] tasks) was assessed over 20 days. Lesion volume and hippocampal neuron survival were quantified on day 21. Additional rats underwent identical CCI and anesthesia with intracranial pressure (ICP) monitoring, and brain water content was assessed. Motor and MWM performances were better in injured rats treated with isoflurane versus fentanyl (p < 0.05). CA1 hippocampal damage was attenuated in isoflurane-treated rats (p < 0.05). Fentanyl-treated rats had higher mean arterial blood pressure after injury (p < 0.05); however, ICP and brain water were similar between groups. Isoflurane improved functional outcome and attenuated damage to CA1 versus fentanyl in rats subjected to CCI. Isoflurane may be neuroprotective by augmenting cerebral blood flow and/or reducing excitotoxicity, not by reducing ICP or brain water content. Alternatively, fentanyl may be detrimental. Isoflurane may mask beneficial effects of novel agents tested in TBI models. Additionally, fentanyl may not be optimal early after TBI in humans.

NOC/oFQ contributes to age-dependent impairment of NMDA-induced cerebrovasodilation after brain injury

This study characterized the effects of fluid percussion brain injury (FPI) on N-methyl-D-aspartate (NMDA)-induced vasodilation and determined the role of nociceptin/orphanin FQ (NOC/oFQ) in such changes as a function of age and time postinsult. FPI elevated cerebrospinal fluid (CSF) NOC/oFQ from 70 +/- 3 to 444 +/- 56 pg/ml ( approximately 10(-10) M) within 1 h and to 1,931 +/- 112 pg/ml within 8 h, whereas values returned to control levels within 168 h in the newborn pig. In contrast, FPI elevated CSF NOC/oFQ from 77 +/- 4 to 202 +/- 16 pg/ml within 1 h and values returned to control levels within 8 h in the juvenile pig. Topical NOC/oFQ (10(-10) M) had no effect on pial artery diameter but attenuated NMDA (10(-8), 10(-6) M)-induced dilation (9 +/- 1 and 16 +/- 1 vs. 5 +/- 1 and 10 +/- 1%) in both age groups. In the newborn, NMDA-induced pial artery dilation was reversed to vasoconstriction within 1 h post-FPI and responses remained impaired for 72 h, but such vasoconstriction was attenuated by pretreatment with [F/G]NOC/oFQ(1-13)-NH(2) (10(-6) M, 1 mg/kg iv), an NOC/oFQ antagonist (9 +/- 1 and 16 +/- 1 vs. -7 +/- 1 and -12 +/- 1 vs -2 +/- 1 and -3 +/- 1% for control, FPI, and FPI pretreated with the NOC/oFQ antagonist). In contrast, in the juvenile, NMDA-induced vasodilation was only attenuated within 1 h post-FPI and returned to control within 8 h. Such dilation was also partially restored by the NOC/oFQ antagonist. These data indicate that NOC/oFQ contributes to impaired NMDA pial artery dilation after FPI. These data suggest that the greater NOC/oFQ release in the newborn versus the juvenile may contribute to age-related differences in FPI effects on excitatory amino acid-induced pial dilation.

Post-traumatic amnesia after closed head injury: a review of the literature and some suggestions for further research

Post-traumatic amnesia (PTA) is a transient sequela of closed head injury (CHI). The term PTA has been in clinical use for over half a century, and generally refers to the subacute phase of recovery immediately after unconsciousness following CHI. The duration of PTA predicts functional outcome after CHI, but its pathophysiological mechanism is not known. This paper compares current methods of determining the duration of PTA, summarizes reports on neuropsychological deficits in PTA, reviews available data that allow inferences about its mechanism, and suggests methods for further exploration of its pathophysiology.

Role of nociceptin/orphanin FQ in age-dependent cerebral hemodynamic effects of brain injury

This study was designed to compare the role of the newly described endogenous opioid nociceptin/orphanin FQ (NOC/oFQ) in the reductions of cerebral blood flow (CBF) and pial artery diameter observed following fluid percussion brain injury (FPI) in chloralose anesthetized newborn and juvenile pigs as a function of time postinsult. FPI elevated CSF NOC/oFQ concentration from 70 +/- 3 to 444 +/- 51 within 1 h and to 1,931 +/- 112 pg/mL (n = 7) within 8 h, whereas concentrations returned to control value within 168 h in the newborn. In contrast, FPI elevated CSF NOC/oFQ from 77 +/- 4 to 202 +/- 16 pg/mL (n = 7) within 1 h, while values returned to control value within 8 h in the juvenile. Topical NOC/oFQ (10(-8), 10(-6) M) induced vasodilation was reversed to vasoconstriction by FPI in the newborn while such responses were only attenuated in the juvenile at 1 h post insult (control, 9 +/- 1 and 16 +/- 1%; FPI newborn, -8 +/- 1 and -14 +/- 1%; FPI juvenile, 2 +/- 1 and 5 +/- 1%, n = 7). Such altered dilation returned to control value within 168 h in newborns and 8 h in juveniles. Blood flow in the cerebrum was reduced from 57 +/- 4 to 23 +/- 3 mL x min(-1) x 100 g(-1) (n = 7) within 1 h and returned to control value with 168 h post FPI in newborns. In animals pretreated with [F/G] NOC/oFQ (1-13) NH2 (1 mg/kg, i.v.), a NOC/oFQ antagonist, however, CBF only fell to 39 +/- 4 mL x min(-1) x 100 g(-1) (n = 7) at 1 h post insult in newborns. In contrast, CBF was only reduced from 57 +/- 6 to 32 +/- 2 in untreated and to 39 +/- 3 mL/min(-1) x 100 g(-1) (n = 7) in treated juveniles within 1 h post FPI. Similar observations for reductions in pial artery diameter were made in untreated and treated newborns and juveniles. These data suggest that an elevated CSF NOC/oFQ concentration and altered vascular responsiveness to this opioid contribute to reductions in CBF and pial artery diameter observed following FPI. Because such NOC/oFQ changes were greater in newborns versus juveniles, these data further suggest that NOC/oFQ contributes to age-related cerebral hemodynamic differences in the effects of FPI.

Neuroprotective effects of a novel NMDA antagonist, Gacyclidine, after experimental contusive spinal cord injury in adult rats

The aim of this study was to analyze the optimal time-window for neuroprotection by a novel NMDA antagonist, Gacyclidine, after experimental spinal cord injury, in terms of its functional, histopathological and electrophysiological effects. This molecule has already demonstrated its capacity for reducing the extent of an ischemic lesion and is currently experimented in a clinical trial of spinal cord injury. In this study, the spinal cord of rats was damaged by a contusive method and the animals were treated by saline or 1 mg/kg of Gacyclidine i.v., 10, 30, 60 and 120 min after injury. The time-course of the motor score was evaluated on days 1, 7 and 18 after injury, and somatosensory evoked potentials were determined on day 20. The animals were then killed and the cross-sectional area of the spinal cord (at the epicenter of the injury, above and below the injury), was measured. Walking recovery was better (P<0.0125) in the group treated 10 min after injury than in the untreated injured animals after 18 days of injury. Motor performances were related to the preservation of a larger undamaged area of spinal cord at the level of the injury (P<0.0125). Somatosensory evoked potential amplitudes were also higher in this group. These results confirm that Gacyclidine attenuates spinal cord damage after an experimental spinal cord lesion. Recovery was better within the group treated 10 min after injury compared with the other groups, which certainly confirms that the acute time-course of glutamate release requires rapid pharmacological intervention to achieve good results.

Superoxide generation links nociceptin/orphanin FQ (NOC/oFQ) release to impaired N-methyl-D-aspartate cerebrovasodilation after brain injury

BACKGROUND AND PURPOSE

Although activation of the N-methyl-D-aspartate (NMDA) receptor is thought to contribute to altered cerebrovascular regulation after traumatic brain injury, the effects of such injury on the vascular response to NMDA itself has been less well appreciated. The newly described opioid nociceptin/orphanin FQ (NOC/oFQ) elicits pial artery dilation, at least in part, in a prostaglandin-dependent manner and is released into cerebrospinal fluid after fluid percussion brain injury (FPI). Generation of superoxide anion (O(2)(-)) occurs after FPI, and a byproduct of cyclooxygenase metabolism is the generation of O(2)(-). This study was designed to determine whether NOC/oFQ generates O(2)(-), which in turn could link NOC/oFQ release to impaired NMDA-induced pial artery dilation after FPI.

METHODS

Injury of moderate severity (1.9 to 2.1 atm) was produced by the lateral FPI technique in anesthetized newborn pigs equipped with a closed cranial window. Superoxide dismutase-inhibitable nitroblue tetrazolium (NBT) reduction was determined as an index of O(2)(-) generation.

RESULTS

Under non-brain injury conditions, topical NOC/oFQ (10(-)(10) mol/L, the concentration present in cerebrospinal fluid after FPI) increased superoxide dismutase-inhibitable NBT reduction from 1+/-1 to 20+/-3 pmol/mm(2) but had no effect itself on pial artery diameter. Indomethacin (5 mg/kg IV) blunted such NBT reduction (1+/-1 to 6+/-2 pmol/mm(2)), whereas the NOC/oFQ receptor antagonist [F/G] NOC/oFQ (1-13) NH(2) (10(-)(6) mol/L) blocked NBT reduction. [F/G] NOC/oFQ (1-13) NH(2) and indomethacin also blunted the NBT reduction observed after FPI (1+/-1 to 15+/-1 versus 1+/-1 to 4+/-1 versus 1+/-1 to 4+/-1 pmol/mm(2) for sham, NOC/oFQ antagonist, and indomethacin-treated animals, respectively). NMDA (10(-)(8) and 10(-)(6) mol/L)-induced pial artery dilation was reversed to vasoconstriction after FPI, and [F/G] NOC/oFQ (1-13) NH(2) attenuated such vasoconstriction (sham 9+/-1% and 16+/-1% versus FPI -7+/-1% and -12+/-1% versus FPI-[F/G] NOC/oFQ (1-13) NH(2)-pretreated animals -2+/-1% and -3+/-1%). Indomethacin and the free radical scavengers polyethylene glycol superoxide dismutase and catalase also partially restored NMDA-induced vasodilation.

CONCLUSIONS

These data show that NOC/oFQ, in concentrations present in cerebrospinal fluid after FPI, increased O(2)(-) production in a cyclooxygenase-dependent manner and contributes to such production after FPI. These data show that NOC/oFQ contributes to impaired NMDA-induced pial artery dilation after FPI. Therefore, these data suggest that cyclooxygenase-dependent O(2)(-) generation links NOC/oFQ release to impaired NMDA-induced cerebrovasodilation after brain injury.

Autoimmune T cells retard the loss of function in injured rat optic nerves

We recently demonstrated that autoimmune T cells protect neurons from secondary degeneration after central nervous system (CNS) axotomy in rats. Here we show, using both morphological and electrophysiological analyses, that the neuroprotection is long-lasting and is manifested functionally. After partial crush injury of the rat optic nerve, systemic injection of autoimmune T cells specific to myelin basic protein significantly diminished the loss of retinal ganglion cells and conducting axons, and significantly retarded the loss of the visual response evoked by light stimulation. These results support our challenge to the traditional concept of autoimmunity as always harmful, and suggest that in certain situations T cell autoimmunity may actually be beneficial. It might be possible to employ T cell intervention to slow down functional loss in the injured CNS.

Effects of chronic ethanol administration on expression of BDNF and trkB mRNAs in rat hippocampus after experimental brain injury

Previous evidence indicates that both chronic alcohol treatment and traumatic brain injury modulate expression of certain neurotrophins and neurotrophin receptors in cortical tissue. However, the combined effects of chronic alcohol and brain trauma on expression of neurotrophins and their receptors have not been investigated. In the present study, we examined the effects of 6 weeks of chronic ethanol administration on lateral fluid percussion (FP) brain injury-induced alterations in expression of mRNAs for the neurotrophin brain-derived neurotrophic factor (BDNF) and its high affinity receptor, trkB, in rat hippocampus. In both the control- (pair-fed isocaloric sucrose) diet and the chronic ethanol-diet groups, unilateral FP brain injury induced a bilateral increase in levels of both BDNF and trkB mRNAs in the dentate gyrus granule cell layer, and of BDNF mRNA in hippocampal region CA3. However, no significant differences in expression were found between the control-diet and ethanol-diet groups, in either the sham-injured or FP-injured animals. These findings suggest that 6 weeks of chronic ethanol administration does not alter the plasticity of hippocampal BDNF/trkB expression in response to experimental brain injury.

Autoimmunity can benefit self-maintenance

Autoimmunity is usually considered only as a cause of disease; nevertheless, human T-cell repertoires are filled naturally with autoimmune lymphocytes. Here, we review evidence that autoimmune T cells can help heal damaged tissues, indicating that natural autoimmunity could also be a cause of health.