Acute, transient hemorrhagic hypotension does not aggravate structural damage or neurologic motor deficits but delays the long-term cognitive recovery following mild to moderate traumatic brain injury.

OBJECTIVES: Posttraumatic hypotension is believed to increase morbidity and mortality in traumatically brain-injured patients. Using a clinically relevant model of combined traumatic brain injury with superimposed hemorrhagic hypotension in rats, the present study evaluated whether a reduction in mean arterial blood pressure aggravates regional brain edema formation, regional cell death, and neurologic motor/cognitive deficits associated with traumatic brain injury. DESIGN: Experimental prospective, randomized study in rodents. SETTING: Experimental laboratory at a university hospital. SUBJECTS: One hundred nineteen male Sprague-Dawley rats weighing 350-385 g. INTERVENTIONS: Experimental traumatic brain injury of mild to moderate severity was induced using the lateral fluid percussion brain injury model in anesthetized rats (n = 89). Following traumatic brain injury, in surviving animals one group of animals was subjected to pressure-controlled hemorrhagic hypotension, maintaining the mean arterial blood pressure at 50-60 mm Hg for 30 mins (n = 47). The animals were subsequently either resuscitated with lactated Ringer's solution (three times shed blood volume, n = 18) or left uncompensated (n = 29). Other groups of animals included those with isolated traumatic brain injury (n = 34), those with isolated hemorrhagic hypotension (n = 8), and sham-injured control animals receiving anesthesia and surgery alone (n = 22). MEASUREMENTS AND MAIN RESULTS: The withdrawal of 6-7 mL of arterial blood significantly reduced mean arterial blood pressure by 50% without decreasing arterial oxygen saturation or Pao2. Brain injury induced significant cerebral edema (p < .001) in vulnerable brain regions and cortical tissue loss (p < .01) compared with sham-injured animals. Neither regional brain edema formation at 24 hrs postinjury nor the extent of cortical tissue loss assessed at 7 days postinjury was significantly aggravated by superimposed hemorrhagic hypotension. Brain injury-induced neurologic deficits persisted up to 20 wks after injury and were also not aggravated by the hemorrhagic hypotension. Cognitive dysfunction persisted for up to 16 wks postinjury. The superimposition of hemorrhagic hypotension significantly delayed the time course of cognitive recovery. CONCLUSIONS: A single, acute hypotensive event lasting 30 mins did not aggravate the short- and long-term structural and motor deficits but delayed the speed of recovery of cognitive function associated with experimental traumatic brain injury.

Delayed transplantation of human neurons following brain injury in rats: a long-term graft survival and behavior study.

The NTera2 (NT2) cell line is a homogeneous population of cells, which, when treated in vitro with retinoic acid, terminally differentiate into postmitotic neuronal NT2N cells. Although NT2N neurons transplanted in the acute (24 h postinjury) period survive for up to 1 month following experimental traumatic brain injury (TBI), nothing is known of their ability to survive for longer periods or of their effects when engrafted during the chronic postinjury period. Adult male Sprague-Dawley rats (n = 348; 360-400 g) were initially anesthetized and subjected to severe lateral fluid-percussion (FP) brain injury or sham injury. At 1 month postinjury, only brain-injured animals showing severe neurobehavioral deficits received cryopreserved NT2N neurons stereotaxically transplanted into three sites in the peri-injured cortex (n = 18). Separate groups of similarly brain-injured rats received human fibroblast cells (n = 13) or cell suspension vehicle (n = 14). Sham-injured animals (no brain injury) served as controls and received NT2N transplants (n = 24). All animals received daily immunosuppression for three months. Behavioral testing was performed at 1, 4, 8, and 12 weeks post-transplantation, after which animals were sacrificed for histological analysis. Nissl staining and anti-human neuronal specific enolase (NSE) immunostaining revealed that NT2N neurons transplanted in the chronic post-injury period survived up to 12 weeks post-transplantation, extended processes into the host cortex and immunolabeled positively for synaptophysin. There were no statistical differences in cognitive or motor function among the transplanted brain-injured groups. Long-term graft survival suggests that NT2N neurons may be a viable source of neural cells for transplantation after TBI and also that these grafts can survive for a prolonged time and extend processes into the host cortex when transplanted in the chronic post-injury period following TBI.

Administration of monoclonal antibodies neutralizing the inflammatory mediators tumor necrosis factor alpha and interleukin -6 does not attenuate acute behavioral deficits following experimental traumatic brain injury in the rat.

PURPOSE: Although many previous studies have indicated that the acute inflammatory response following traumatic brain injury (TBI) is detrimental, inflammation may also positively influence outcome in the more chronic post-injury recovery period. We evaluated the effects of monoclonal antibodies (mAB), neutralizing either IL-6 (IL-6 mAB) or TNF-alpha (TNF mAB), administered intracerebroventricularly (i.c.v) on acute neurobehavioral outcome following TBI. METHODS: Male Sprague-Dawley rats (n = 173) were anesthetized (sodium pentobarbital, 60 mg/kg) and subjected to lateral fluid percussion (FP) brain injury of moderate severity (n = 123) or sham injury (n = 50). Beginning 1 h post-injury, TNF mAB (n = 41, of which 25 were brain-injured) or IL-6 mAB (n = 42, of which 25 were brain-injured) at a concentration of 2 mg/mL was infused i.c.v ipsilateral to the injury for 48 hours. Vehicle-treated animals (control IgG; n = 43, of which 26 were brain-injured) served as controls. In Study 1, cognitive function was evaluated in the Morris Water Maze (MWM) followed by evaluation of regional cerebral edema at 48 h post-injury. In Study 2, animals were evaluated for neurological motor function and post-injury learning in the MWM at one week post-injury. RESULTS: FP brain injury caused significant cognitive (p < 0.05) and neurological motor (p < 0.05) deficits and increased regional brain water content in the injured hemisphere. Treatment with either TNF- or IL-6-mAB had no effect on neurological motor, cognitive function or brain edema during the first post-injury week. CONCLUSIONS: Evaluation of anti-inflammatory mABs on more chronic behavioral deficits appears warranted.

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.