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.

Development of posttraumatic hyperthermia after traumatic brain injury in rats is associated with increased periventricular inflammation.

Posttraumatic hyperthermia (PTH) is a noninfectious elevation in body temperature that negatively influences outcome after traumatic brain injury (TBI). We sought to (1) characterize a clinically relevant model and (2) investigate potential cellular mechanisms of PTH. In study I, body temperature patterns were analyzed for 1 week in male rats after severe lateral fluid percussion (FP) brain injury (n=75) or sham injury (n=17). After injury, 27% of surviving animals experienced PTH, while 69% experienced acute hypothermia with a slow return to baseline. A profound blunting or loss of circadian rhythmicity (CR) that persisted up to 5 days after injury was experienced by 75% of brain-injured animals. At 2 and 7 days after injury, patterns of cell loss and inflammation were assessed in selected brain thermoregulatory and circadian centers. Significant cell loss was not observed, but PTH was associated with inflammatory changes in the hypothalamic paraventricular nucleus (PVN) by one week after injury. In brain-injured animals with altered CR, reactive astrocytes were bilaterally localized in the suprachiasmatic nucleus (SCN) and the PVN. Occasional IL-1beta+/ED-1+ macrophages/microglia were observed in the PVN and SCN exclusively in brain-injured animals developing PTH. In animals with PTH there was a significant positive correlation (r=0.788, P<0.01) between the degree of postinjury hyperthermia and the total number of cells positive for inflammatory markers within selected thermoregulatory and circadian nuclei. In study II, a separate group of animals underwent the same injury and temperature monitoring paradigm as in study I, but had additional physiologic data obtained, including vital signs, arterial blood gases, white blood cell counts, and C-reactive protein levels. All parameters remained within normal ranges after injury. These data suggest that PTH and the alteration in CR of temperature may be due, in part, to acute reactive astrocytosis and inflammation in hypothalamic centers responsible for both thermoregulation and CR.

Inhibition of vascular endothelial growth factor receptor (VEGFR) signaling by BSF476921 attenuates regional cerebral edema following traumatic brain injury in rats.

PURPOSE: In the present study we assessed the ability of BSF476921, an inhibitor of vascular endothelial growth factor receptor (VEGFR) kinase signal transduction, to reduce edema formation and neurologic motor dysfunction following lateral fluid percussion (FP) brain injury in rats. METHODS: Anesthetized adult male rats were subjected to either lateral FP brain injury of moderate severity (n = 37) or sham injury (n = 22, surgery without brain injury). Animals were randomized to receive i.p. injections of either BSF476921 (30 mg/kg bw; injured n = 15, sham n = 11) or sterile water (injured n = 14, sham n = 11) at 1, 11 and 22 hours post-injury. After assessment of motor function using a standard 28-point neuroscore, animals were sacrificed 24 hours following trauma and their brains evaluated for regional water content using the wet-weight/dry-weight technique. RESULTS: Although brain-injured animals showed a significant motor deficit compared to uninjured animals, no differences were detected between BSF476921- and vehicle-treated animals at the acute 24 hour post-injury time point. However, BSF476921 significantly attenuated regional edema formation in brain-injured animals in the ipsilateral hippocampus (p < 0.05) and in the cortex adjacent to the injury (p < 0.05) when compared to vehicle treatment. CONCLUSIONS: To our knowledge, this is the first report of a small molecule VEGFR kinase inhibitor reducing cerebral edema in a widely accepted model of brain injury.

Differential effects of the anticonvulsant topiramate on neurobehavioral and histological outcomes following traumatic brain injury in rats.

The efficacy of topiramate, a novel therapeutic agent approved for the treatment of seizure disorders, was evaluated in a model of traumatic brain injury (TBI). Adult male rats were anesthetized (sodium pentobarbital, 60 mg/kg, i.p.), subjected to lateral fluid percussion brain injury (n = 60) or sham injury (n = 47) and randomized to receive either topiramate or vehicle at 30 min (30 mg/kg, i.p.), and 8, 20 and 32 h postinjury (30 mg/kg, p.o.). In Study A, memory was evaluated using a Morris water maze at 48 h postinjury, after which brain tissue was evaluated for regional cerebral edema. In Study B, animals were evaluated for motor function at 48 h and 1, 2, 3, and 4 weeks postinjury using a composite neuroscore and the rotating pole test and for learning ability at 4 weeks. Brains were analyzed for hemispheric tissue loss and hippocampal CA3 cell loss. Topiramate had no effect on posttraumatic cerebral edema or histologic damage when compared to vehicle. At 48 h, topiramate treatment improved memory function in sham but not brain-injured animals, while at one month postinjury it impaired learning performance in brain-injured but not sham animals. Topiramate significantly improved composite neuroscores at 4 weeks postinjury and rotating pole performance at 1 and 4 weeks postinjury, suggesting a potentially beneficial effect on motor function following TBI.