Tomas Winkler

Evaluation of traumatic spinal cord edema using evoked potentials recorded from the spinal epidural space: An experimental study in the rat

Spinal cord evoked potentials (SCEP) elicited by simultaneous distal tibial and sural nerve stimulation were continuously recorded from the epidural space at the T9 and T12 levels of urethane anaesthetized rats before and after a unilateral incision (about 3 mm deep and 5 mm long) in the right dorsal horn of the T10-11 segments. The changes in SCEP were correlated with the increase in spinal cord water content measured 5 h after injury. In addition, the influence of serotonin (5-HT) in mediating such changes was explored using a pharmacological approach. The changes in SCEP immediately after injury correlated well with development of spinal cord edema measured 5 h after injury. Thus, the maximal negative peak (MNP) amplitude of SCEP decreased by an average of 64.0% immediately after injury and the water content of the spinal cord was increased from 71.6% (controls) to 77.6% 5 h after injury. Pretreatment with p-CPA (a serotonin synthesis inhibitor) prevented the initial decrease of the MNP amplitude and also the increase of water content (72.5%). On the other hand, pretreatment with cyproheptadine (a 5-HT2 receptor antagonist) enhanced both the initial decrease of the MNP amplitude as well as the increase of water content (81.3%). The results show a good correlation between changes of SCEP immediately after injury and the magnitude of spinal cord edema (r = 0.9) measured 5 h after injury. The findings reveal a major role of serotonin in mediating early changes of SCEP and later development of spinal cord edema and demonstrate a prognostic value of early SCEP recordings in predicting the final outcome of traumatic spinal cord injuries.

Topical application of TNF-α antiserum attenuates spinal cord trauma induced edema formation, microvascular permeability disturbances and cell injury in the rat

The possibility that antiserum to tumour necrosis factor-alpha (TNF-alpha) is neuroprotective in spinal cord injury (SCI) was examined in a rat model. SCI was produced by making an incision into the right dorsal horn at the T10-11 segments. Top TNF-alpha antiserum at three concentrations (1:10; 1:50 and 1:100) given 30 min before or 2 min, 5 min or 10 min after trauma resulted in marked reduction in visible swelling, edema formation, and leakage of radiolabelled iodine tracer within the T9 and T12 segments at 5 h in a dose dependent manner. This neuroprotective effect was most pronounced when the antiserum at the highest dose level (1:10) was applied 10 min after SCI. The TNF-alpha antiserum also reduced the SCI induced upregulation of neuronal nitric oxide synthase (nNOS) immunoreactivity in a concentration dependent manner. Taken together, these results suggest that local application of TNF-alpha antiserum is neuroprotective in SCI and that this effect is mediated through NOS regulation.

Opioid receptors influence spinal cord electrical activity and edema formation following spinal cord injury: experimental observations using naloxone in the rat

The possibility that opioid peptides participate in alteration of spinal cord conduction following trauma to the cord was investigated in a rat model using a pharmacological approach. Spinal cord injury was produced in urethane anesthetized animals by a longitudinal incision into the right dorsal horn of T10-11 segments (2 mm deep and 5 mm long). Spinal cord evoked potentials (SCEP) were recorded epidurally from the T9 (rostral) and T12 (caudal) segments after stimulation of the ipsilateral tibial and sural nerves at the ankle. SCEP from both rostral and caudal segments consisted of a small positive peak followed by a high negative peak. Infliction of trauma in untreated rats resulted in an immediate depression of the rostral maximal negative peak (MNP) amplitude. This depression was long-lasting. Later, a significant increase in the latency of the rostral MNP amplitude occurred. Naloxone was administered in a high dosage (10 mg/kg, i.p.) to block mu-, delta- and kappa-opioid receptors 30 min before injury. This drug treatment inhibited the immediate post-injury decrease of the rostral MNP amplitude without any significant effect on latency changes. Measurement of water content in the traumatized spinal cord segment showed a significant reduction in the drug treated animals 5 h after trauma (71.46 +/- 0.54) as compared with untreated controls (74.65 +/- 0.76). However, 1 mg or 5 mg/kg dosages of the drug were not effective in reducing the SCEP changes or edema after injury. These results strongly suggest that blockade of kappa-opioid receptors with high doses of naloxone is important in reduction of trauma induced alteration of SCEP and edema formation in spinal cord injury.

Assessment of spinal cord pathology following trauma using early changes in the spinal cord evoked potentials: A pharmacological and morphological study in the rat

The possibility that spinal cord pathology following trauma can be assessed with early changes in the spinal cord evoked potentials (SCEPs) was examined in a rat model. Spinal cord injury (SCI) was produced in Equithesin‐anesthetized (3 ml/kg, i.p.) rats through a longitudinal incision into the right dorsal horn at the T10–11 segments. The SCEPs were recorded with epidural electrodes placed over the T9 (rostral) segment of the cord. The SCEPs consisted of a small positive amplitude and a broad and high negative amplitude (NA). SCI resulted in an instant depression of the rostral NA that lasted for 1 h. However, the latency of NA continued to increase over time. At 5 h, spinal cord blood flow declined by 30% in the T9 segment, whereas the spinal cord water content and the permeability of the blood–spinal cord barrier (BSCB) were markedly increased. Damage to the nerve cells, glial cells, and myelin was quite common in the spinal cord, as seen by light and electron microscopy. Pretreatment with p‐chlorophenylalanine, indomethacin, ibuprofen, and nimodipine attenuated the SCEP changes immediately after trauma and resulted in a marked reduction in edema formation, BSCB permeability, and blood flow changes at 5 h. However, pretreatment with cyproheptadine, dexamethasone, phentolamine, and propranolol failed to attenuate the SCEP changes after SCI and did not reduce the cord pathology. These observations suggest that early changes in SCEP reflect secondary injury‐induced alterations in the cord microenvironment. Obviously, these changes are crucial in determining the ultimate magnitude and severity of cord pathology.

An L-type calcium channel blocker, nimodipine influences trauma induced spinal cord conduction and axonal injury in the rat

The influence of the potent L-type Ca[2+] channel antagonist Nimodipine on spinal cord evoked potentials (SCEP) and axonal injury following trauma to the spinal cord was examined in a rat model. Spinal cord injury (SCI) was produced by an incision into the right dorsal horn of the T10-11 segments under urethane anaesthesia (1.5 g/kg, i.p.). SCEPs were recorded by epidural electrodes placed over the T9 (rostral) and T12 (caudal) segments after stimulation of the right tibial and sural nerves. SCI induced a pronounced decrease of the SCEP negative amplitude in the rostral (T9) recordings immediately after trauma. Axonal injury seen as degradation of myelin basic protein (MBP) immunostaining and myelin vesiculation at the ultrastructural level was most pronounced at 5 h. Continuous administration of Nimodipine (2 microg/kg/min, i.v.) from 30 min prior to injury until sacrifice markedly attenuated the changes in SCEP amplitude and latency. Axonal damage, loss of MBP, and myelin vesiculation were much less evident in the nimodipine treated traumatised rats. These observations suggest that Ca[2+] channels play an important role in the trauma induced alterations in SCEP and axonal injury, and indicate a therapeutic value of Ca[2+] blockers in SCI.

p-Chlorophenylalanine, an Inhibitor of Serotonin Synthesis Reduces Blood-Brain Barrier Permeability, Cerebral Blood Flow, Edema Formation and Cell Injury Following Trauma to the Rat Brain

The role of serotonin in trauma induced alterations in blood-brain barrier (BBB) permeability, cerebral blood flow (CBF), brain edema and cell changes were examined in a new model of cortical injury in the rat using a pharmacological approach. A longitudinal incision into the right parietal cerebral cortex (about 3 mm deep and 5 mm long) was associated with a profound increase in the BBB permeability to Evans blue and [131]I-sodium, brain water content, and a reduction in the CBF in both the ipsilateral and contralateral hemispheres 5 h after trauma. Nissl staining showed a profound nerve cell reaction in the parietal cerebral cortex of both hemispheres. The intensity of these pathological changes was most pronounced in the traumatised hemisphere. Pretreatment with p-CPA, a serotonin synthesis inhibitor, significantly attenuated breakdown of the BBB permeability, brain edema and the CBF disturbances. Damaged and distorted nerve cells were markedly less frequent in p-CPA treated rats. This effect of the drug was most pronounced in the contralateral hemisphere. The observations strongly suggest that serotonin is one of the important neurochemical mediators of BBB permeability disturbances and brain edema formation in the trauma induced brain damage.

Neurotrophic factors attenuate alterations in spinal cord evoked potentials and edema formation following trauma to the rat spinal cord.

Influence of brain derived neurotrophic factor (BDNF) and insulin like growth factor-1 (IGF-1) on spinal cord injury induced disturbances in spinal cord conduction, edema formation and cellular stress response was examined in a rat model. Pretreatment with BDNF or IGF-1 significantly attenuated the loss of SCEP negative amplitude seen immediately after spinal cord injury. In these neurotrophins treated rats, upregulation of heat shock protein (HSP 72 kD) immunoreactivity, a measure of cellular stress response and spinal cord edema formation were considerably reduced 5 h after injury. These results suggest that neurotrophic factors improve spinal cord conduction after trauma and this beneficial effect of growth factors may be related with their ability to attenuate trauma induced cellular stress response, not reported earlier.

Naloxone reduces alterations in evoked potentials and edema in trauma to the rat spinal cord.

The influence of naloxone (an opioid receptor antagonist) on spinal cord conduction and edema formation as a result of trauma to the cord was investigated in a rat model. The spinal cord injury (SCI) was inflicted in urethane anesthetized animals by a longitudinal incision into the right dorsal horn of the T10-11 segments, about 2 mm deep and 5 mm long. Spinal cord evoked potentials (SCEP) were recorded epidurally from the T9 (rostral) and T12 (caudal) segments after stimulation of the ipsilateral tibial and sural nerves at the ankle. The edema was measured by determining water content of the cord at s h after injury. In rats not given naloxone SCI resulted in an immediate long-lasting depression of the rostral maximal negative peak (MNP) amplitude (about 60%) and a significant increase in the latency of the rostral maximal positive peak (MPP). Pretreatment with naloxone inhibited the immediate post-injury decrease of the rostral MNP and some of the increase of MPP latency. The water content in the traumatized spinal cord was reduced by 3% in naloxone treated animals compared with untreated injured controls. Our results indicate that endogenous opioid peptides participate in changes of spinal cord conduction after trauma and influence edema formation probably via multiple opioid receptors.

Benzodiazepine receptors influence spinal cord evoked potentials and edema following trauma to the rat spinal cord.

The possibility that diazepam will influence spinal cord evoked potentials (SCEP), edema formation and cell changes following spinal cord injury (SCI) was examined in a rat model. The SCI was produced in equithesin anaesthetised animals by making a longitudinal incision (about 2 mm deep and 5 mm long) in the right dorsal horn of the T10-11 segments. The SCEP were recorded from the epidural space of the T9 segment after stimulation of the right tibial and sural nerves. The SCEP consisted of a small positive peak followed by a broad and high negative peak. Infliction of trauma to the rats resulted in an immediate and pronounced decrease of the maximal negative peak (MNP) amplitude. The spinal cord edema and cell changes were markedly pronounced 5 h after injury. Pretreatment with diazepam attenuated the early SCEP changes induced by the trauma and reduced the later development of edema and cell injury. These results suggest that benzodiazepine receptors are involved in trauma induced alterations in SCEP changes, edema formation and cell injury, not reported earlier.