Serotonin in contused spinal cord

Iron oxide nanoparticles and magnetic field exposure promote functional recovery by attenuating free radical-induced damage in rats with spinal cord transection

BACKGROUND

Iron oxide nanoparticles (IONPs) can attenuate oxidative stress in a neutral pH environment in vitro. In combination with an external electromagnetic field, they can also facilitate axon regeneration. The present study demonstrates the in vivo potential of IONPs to recover functional deficits in rats with complete spinal cord injury.

METHODS

The spinal cord was completely transected at the T11 vertebra in male albino Wistar rats. Iron oxide nanoparticle solution (25 μg/mL) embedded in 3% agarose gel was implanted at the site of transection, which was subsequently exposed to an electromagnetic field (50 Hz, 17.96 μT for two hours daily for five weeks).

RESULTS

Locomotor and sensorimotor assessment as well as histological analysis demonstrated significant functional recovery and a reduction in lesion volume in rats with IONP implantation and exposure to an electromagnetic field. No collagenous scar was observed and IONPs were localized intracellularly in the immediate vicinity of the lesion. Further, in vitro experiments to explore the cytotoxic effects of IONPs showed no effect on cell survival. However, a significant decrease in H2O2-mediated oxidative stress was evident in the medium containing IONPs, indicating their free radical scavenging properties.

CONCLUSION

These novel findings indicate a therapeutic role for IONPs in spinal cord injury and other neurodegenerative disorders mediated by reactive oxygen species.

Spinal cord contusion models

Most human spinal cord injuries involve contusions of the spinal cord. Many investigators have long used weight-drop contusion animal models to study the pathophysiology and genetic responses of spinal cord injury. All spinal cord injury therapies tested to date in clinical trial were validated in such models. In recent years, the trend has been towards use of rats for spinal cord injury studies. The MASCIS Impactor is a well-standardized rat spinal cord contusion model that produces very consistent graded spinal cord damage that linearly predicts 24-h lesion volumes, 6-week white matter sparing, and locomotor recovery in rats. All aspects of the model, including anesthesia for male and female rats, age rather than body weight criteria, and arterial blood gases were empirically selected to enhance the consistency of injury.

Acute aggregation of serotonin-immunoreactive platelets in the injured spinal cord of rat and change of serotonin content in the neural fibers

Serotonin (5-HT) immunoreactivity was investigated at the injury site of the rat spinal cord by light and electron microscopic immunohistochemistry. The animals were perfused with fixative immediately, 1-5 min, 7-60 min, and 1-48 h after a 3-sec extradural compression of the thoracic cord with a Sugita aneurysm clip. Five minutes after injury, abundant hemostatic plugs containing platelets with high 5-HT immunoreactivity appeared at the traumatized cord segment, whereas 5-HT-containing varicose fibers became less immunoreactive. The 5-HT-immunoreactive platelets initially were localized to the periphery of the hemostatic plugs. By 30 min after injury, the platelets had decreased 5-HT, but neural fibers and terminals began to show increased 5-HT immunoreactivity, which increased and lasted as long as 48 h. These results indicate that platelets contributed to the initial 5-HT concentration increase at the injury site but that later 5-HT accumulation occurred in the neural elements.

Self-biting with multiple finger amputations following spinal cord injury

We have observed mutilative self-biting leading to multiple finger amputations in two patients following C4 complete spinal cord injury (SCI). Both men were of normal intelligence without psychosis and each had a neurotic personality and history of fingernail biting. They related the self-biting to anxiety and depression. We believe these to be the first English language reports of multiple finger amputations due to self-biting following SCI.

Effect of aminophylline and isoproterenol on spinal cord blood flow after impact injury

A study of the effects of spinal cord injury upon spinal cord blood flow was carried out in cats. A 400 mg-cm impact produced an overall reduction in spinal cord blood flow of 24% in the white matter and 30% in the gray matter, as determined by 14C-antipyrine autoradiography. At the level of the injury, white-matter flow was 8.1 ml/100 gm/min, a reduction of 49%, and in the gray matter, 12.5 ml/100 gm/min, a reduction of 76%. Treatment with aminophylline and isoproterenol improved the overall blood flow in the spinal cord. At the level of the injury, white-matter flow after this treatment was no longer significantly different from control values. The gray-matter flow remained decreased to 26.2 ml/100 gm/min, a reduction of only 47%. It is proposed that aminophylline and isoproterenol may increase cyclic adenosine monophosphate (AMP) and prevent platelet aggregation along the endothelial surfaces of the microcirculation, and may thereby help to maintain improved perfusion of the injured spinal cord.