The effect of acute cocaine or lidocaine on behavioral function following fluid percussion brain injury in rats

Natural Compounds as a Therapeutic Intervention following Traumatic Brain Injury: The Role of Phytochemicals

There has been a tremendous focus on the discovery and development of neuroprotective agents that might have clinical relevance following traumatic brain injury (TBI). This type of brain injury is very complex and is divided into two major components. The first component, a primary injury, occurs at the time of impact and is the result of the mechanical insult itself. This primary injury is thought to be irreversible and resistant to most treatments. A second component or secondary brain injury, is defined as cellular damage that is not immediately obvious after trauma, but that develops after a delay of minutes, hours, or even days. This injury appears to be amenable to treatment. Because of the complexity of the secondary injury, any type of therapeutic intervention needs to be multi-faceted and have the ability to simultaneously modulate different cellular changes. Because of diverse pharmaceutical interactions, combinations of different drugs do not work well in concert and result in adverse physiological conditions. Research has begun to investigate the possibility of using natural compounds as a therapeutic intervention following TBI. These compounds normally have very low toxicity and have reduced interactions with other pharmaceuticals. In addition, many natural compounds have the potential to target numerous different components of the secondary injury. Here, we review 33 different plant-derived natural compounds, phytochemicals, which have been investigated in experimental animal models of TBI. Some of these phytochemicals appear to have potential as possible therapeutic interventions to offset key components of the secondary injury cascade. However, not all studies have used the same scientific rigor, and one should be cautious in the interpretation of studies using naturally occurring phytochemical in TBI research.

Effect of cocaine use on outcomes in traumatic brain injury

Context:

Animal and molecular studies have shown that cocaine exerts a neuroprotective effect against cerebral ischemia.

Aims:

To determine if the presence of cocaine metabolites on admission following traumatic brain injury (TBI) is associated with better outcomes.

Settings and Design:

Level-1 trauma center, retrospective cohort.

Materials and Methods:

After obtaining Institutional Review Board (IRB) approval, the trauma registry was searched from 2006 to 2009 for all patients aged 15-55 years with blunt head trauma and non-head AIS <3. Exclusion criteria were pre-existing brain pathology and death within 30 min of admission. The primary outcome was in-hospital mortality; secondary outcomes were hospital length of stay (LOS), and Glasgow Outcome Score (GOS).

Statistical Analysis:

Logistic regression was used to determine the independent effect of cocaine on mortality. Hospital LOS was compared with multiple linear regression.

Results:

A total of 741 patients met criteria and had drug screens. The screened versus unscreened groups were similar. Cocaine positive patients were predominantly African-American (46% vs. 21%, P < 0.0001), older (40 years vs. 30 years, P < 0.0001), and had ethanol present more often (50.7% vs. 37.8%, P = 0.01). There were no differences in mortality (cocaine-positive 1.4% vs. cocaine-negative 2.7%, P = 0.6) on both univariate and multivariate analysis.

Conclusions:

Positive cocaine screening was not associated with mortality in TBI. An effect may not have been detected because of the low mortality rate. LOS is affected by many factors unrelated to the injury and may not be a good surrogate for recovery. Similarly, GOS may be too coarse a measure to identify a benefit.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

The maxi-K channel opener BMS-204352 attenuates regional cerebral edema and neurologic motor impairment after experimental brain injury

Large-conductance, calcium-activated potassium (maxi-K) channels regulate neurotransmitter release and neuronal excitability, and openers of these channels have been shown to be neuroprotective in models of cerebral ischemia. The authors evaluated the effects of postinjury systemic administration of the maxi-K channel opener, BMS-204352, on behavioral and histologic outcome after lateral fluid percussion (FP) traumatic brain injury (TBI) in the rat. Anesthetized Sprague-Dawley rats (n = 142) were subjected to moderate FP brain injury (n = 88) or surgery without injury (n = 54) and were randomized to receive a bolus of 0.1 mg/kg BMS-204352 (n = 26, injured; n = 18, sham), 0.03 mg/kg BMS-204352 (n = 25, injured; n = 18, sham), or 2% dimethyl sulfoxide (DMSO) in polyethylene glycol (vehicle, n = 27, injured; n = 18, sham) at 10 minutes postinjury. One group of rats was tested for memory retention (Morris water maze) at 42 hours postinjury, then killed for evaluation of regional cerebral edema. A second group of injured/sham rats was assessed for neurologic motor function from 48 hours to 2 weeks postinjury and cortical lesion area. Administration of 0.1 mg/kg BMS-204352 improved neurologic motor function at 1 and 2 weeks postinjury (P < 0.05) and reduced the extent of cerebral edema in the ipsilateral hippocampus, thalamus, and adjacent cortex (P < 0.05). Administration of 0.03 mg/kg BMS-204352 significantly reduced cerebral edema in the ipsilateral thalamus (P < 0.05). No effects on cognitive function or cortical tissue loss were observed with either dose. These results suggest that the novel maxi-K channel opener BMS-204352 may be selectively beneficial in the treatment of experimental TBI.

The hemodynamic effects of cocaine during acute controlled hemorrhage in conscious rats

BACKGROUND

Cocaine is often associated with trauma; however, little is known about how its use alters the response to blood loss. The effect of cocaine on hemodynamics following acute hemorrhage was studied in a rat model.

METHODS

Following baseline measurements, rats were administered either intravenous cocaine, or saline as a control. Both groups then underwent arterial catheter hemorrhage of 30% of total blood volume. Outcome variables include blood pressure, heart rate, hematocrit, pH, PCO2, PO2, and serum bicarbonate.

RESULTS

Following hemorrhage, blood pressure decreased in both groups but the hypotension was significantly greater in the saline group than the intravenous cocaine group at 0 and 5 minutes posthemorrhage. Heart rate was increased significantly for the intravenous cocaine group compared to the saline group starting at 15 minutes postcocaine and lasting for the next 25 minutes. No difference was noted for hematocrit, pH, PO2, or serum bicarbonate.

CONCLUSION

Although transient, cocaine blunted the hypotensive response to acute controlled hemorrhage and resulted in tachycardia.

The effect of cocaine on traumatic brain injury outcome: a preliminary evaluation

The effect of acute cocaine use on the functional and neuropsychological outcome of persons with traumatic brain injury, (TBI) was examined by comparing persons with TBI who tested positive for cocaine at the time of admission with persons with negative drug and alcohol screens. Subjects were matched for age, admission GCS score, level of education, and aetiology of injury (closed vs penetrating head injury). Dependent measures were: the Disability Rating Scale, the Functional Independence Measure, and selected neuropsychological tests. No group differences were found in DRS, FIM, FIM subsets, or FIM change. However, the cocaine group scored significantly lower than the no-drug group on the Rey Auditory Verbal Learning Test, but did not differ on any of the other neuropsychological tests.

Mild traumatic lesion of the right parietal cortex of the rat: selective behavioural deficits in the absence of neurological impairment

Fluid impact models are widely used to study the histological and neurochemical consequences of traumatic brain injury and although behavioural consequences have also been studied, behavioural changes are often confounded by non-specific neurological deficits. In the present study we investigated behavioural effects of a unilateral mild traumatic lesion of the right lateral parietal cortex. This region is implicated in a number of basic and complex behaviors, and we therefore analyzed the performance of rats in a diverse range of behavioural procedures. The lesion had no effects on general neurological function, motor activity (activity boxes, rota-rod and paw reaching tests), habituation to a novel environment (holeboard), spatial learning ability (Morris water maze) or anxiety (elevated plus-maze). However, the lesioned animals demonstrated lower levels of exploration than the control group when novel objects were placed beneath some of the holes in the holeboard. Lesioned animals also differed from controls in their performance in passive and active avoidance procedures. In a step-through passive avoidance test the lesioned rats performed worse than the sham-operated controls, i.e. they had significantly lower entry latencies on the 2nd day. In contrast, in the active avoidance task the lesioned animals performed better than sham-operated rats, demonstrating a better ability to learn to avoid and escape from the shock. These diverse results in different tests of learning and memory, in particular the impairment in passive avoidance and the improvement in active avoidance behavior, are difficult to reconcile with a simple effect of the lesion on cognitive performance per se. The complete absence of general neurological deficits following the mild traumatic injury rules out the possibility that the observed behavioural changes reflect a non-specific impairment. These results demonstrate that mild traumatic lesion of the right parietal cortex can induce relatively selective behavioural changes that may serve to study functional recovery after trauma. However further work is required to establish the underlying deficit(s) that has led to the behavioural effects described here.

The 21-aminosteroid U-74389G reduces cerebral superoxide anion concentration following fluid percussion injury of the brain

We examined the effects of the 21-aminosteroid antioxidant U-74389G (16-desmethyl-tirilazad) on the concentration of extracellular superoxide anion following fluid percussion traumatic brain injury (TBI) measured by a cytochrome c-coated electrode and on local cerebral perfusion (CBFld) measured by laser Doppler flowmetry (LDF). U-74389G in a dose of 3 mg/kg reduced superoxide anion concentrations 60 min after TBI significantly but had no significant effect on CBFld. These results indicate that reduction of CBF after TBI can be dissociated from superoxide anion production. Persistent ischemia may limit neuroprotection efficacy and may contribute to divergent outcome results in clinical and animal trials using agents to modify reactive oxygen species.

Is high extracellular glutamate the key to excitotoxicity in traumatic brain injury?

Traumatic brain injury (TBI) increases extracellular levels of the excitatory amino acid glutamate and aspartate, and N-methyl-D aspartate (NMDA)-receptor antagonists protect against experimental TBI. These two findings have led to the prevalent hypothesis that excitatory amino acid efflux is a major contributor to the development of neuronal damage subsequent to traumatic injury. However, as with stroke, the hypothesis that high extracellular glutamate is the key to excitotoxicity in TBI conflicts with important data. For example, the initial increase in extracellular glutamate is cleared within 5 min after moderate TBI, whereas antagonists of glutamate receptors and the so- called presynaptic glutamate release inhibitors remain effective when administered 30 min after insult. In this article, we argue that the current concept of excitotoxicity in TBI, centered on high extracellular glutamate, does not withstand scientific scrutiny. As alternatives to explain the beneficial actions of glutamate antagonists in experimental TBI, we propose abnormalities of glutamatergic neurotransmission, such as deficient Mg2+ block of NMDA-receptor ionophore complexes, and phenomena such as spreading depression, which requires activation of glutamate receptors and is detrimental to neurons in damaged/vulnerable brain regions. Finally, we introduce the notion that beneficial effects of glutamate receptor antagonists in experimental models of neurological disorders do not necessarily imply the occurrence of excitotoxic processes. Indeed, glutamate-receptor blockade may be protective by reducing the energy demand required to counterbalance Na+ influx associated with glutamatergic synaptic transmission. In other words, glutamate receptor antagonists (and blockers of voltage-gated Na+-channels) may help nervous tissue to cope with increased permeability of the cellular membrane to ions and reduced efficacy of Na+ extrusion, and thus prevent the decay of transmembrane ionic concentrations gradients.

The effect of postinjury administration of polyethylene glycol-conjugated superoxide dismutase (pegorgotein, Dismutec) or lidocaine on behavioral function following fluid-percussion brain injury in rats

Previous studies in our laboratory have shown that polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) or lidocaine treatment before experimental fluid-percussion brain injury in rats reduces the cortical hypoperfusion normally found in the early posttraumatic period. The purpose of the current study was to determine if posttreatment with PEG-SOD or lidocaine is also associated with changes in the trauma-induced suppression of motor and cognitive function that occurs following traumatic brain injury (TBI). Twenty-four hours after surgical preparation, rats were randomly assigned to a saline or drug posttreatment group, PEG-SOD (pegorgotein, Dismutec 10,000 IU/kg) or lidocaine (2 mg/kg), which was injected iv 30 min after moderate injury. PEG-SOD completely prevented beam walk deficits on days 1-5 postinjury while lidocaine similarly prevented beam walk deficits on days 2 through 5 postinjury. Both drugs produced a statistically insignificant trend for a decrease in beam balance duration deficits on days 1-5 postinjury and had no effect on cognitive function, as assessed by the Morris water maze, on days 11 through 15 postinjury. The mechanism by which PEG-SOD and lidocaine reduce posttraumatic motor deficits may be related to their free radical scavenging effect or previously reported effects on posttraumatic cerebral blood flow. To our knowledge, this is the first report of the effectiveness of these two agents in laboratory animals when administered after traumatic injury.

Superoxide dismutase improves posttraumatic cortical blood flow in rats

Oxygen free radicals, such as the superoxide anion, are known to mediate damage to the cerebral microcirculation following traumatic brain injury. The purpose of this study was to determine if superoxide dismutase (SOD), a scavenger of superoxide anion, could alter posttraumatic cortical blood flow. Following barbiturate anesthesia, rats were surgically prepared for moderate fluid percussion brain injury. Cortical blood flow contralateral to the site of injury was measured using laser-Doppler flowmetry. Laser-Doppler flowmetry assesses flow by measuring cell volume and velocity, which are multiplied electronically to give flow. Starting 10 min before injury, animals received either superoxide dismutase (24,000 U/kg bolus, followed by continuous infusion of 1600 U/kg/min) or an equal volume of saline. Blood pressure, heart rate, and cortical blood flow were measured up to 1 h posttrauma. Rats receiving superoxide dismutase had significantly higher cortical blood flow posttrauma (F = 6.91, p < 0.02). One hour posttrauma, the blood flow in SOD-treated rats was 89 +/- 8% of preinjury baseline, whereas this value was only 66 +/- 6% of control in saline-treated rats. SOD caused not only greater blood velocity but also less reduction in cortical blood volume after injury. There were no significant differences between the groups with respect to blood pressure or heart rate. This study further supports the role of oxygen radical-mediated cerebrovascular dysfunction following traumatic brain injury and is the first to show the beneficial effect of SOD on cortical blood flow following fluid percussion brain injury.