tetrodotoxin and Craniocerebral-Trauma

Recent experimental and modeling results demonstrated that surviving mossy cells in the dentate gyrus play key roles in the generation of network hyperexcitability. Here we examined if mossy cells exhibit long-term plasticity in the posttraumatic, hyperexcitable dentate gyrus. Mossy cells 1 wk after fluid percussion head injury did not show alterations in their current-firing frequency (I-F) and current-membrane voltage (I-V) relationships. In spite of the unchanged I-F and I-V curves, mossy cells showed extensive modifications in Na(+), K(+) and h-currents, indicating the coordinated nature of these opposing modifications. Computational experiments in a realistic large-scale model of the dentate gyrus demonstrated that individually, these perturbations could significantly affect network activity. Synaptic inputs also displayed systematic, opposing modifications. Miniature excitatory postsynaptic current (EPSC) amplitudes were decreased, whereas miniature inhibitory postsynaptic current (IPSC) amplitudes were increased as expected from a homeostatic response to network hyperexcitability. In addition, opposing alterations in miniature and spontaneous synaptic event frequencies and amplitudes were observed for both EPSCs and IPSCs. Despite extensive changes in synaptic inputs, cannabinoid-mediated depolarization-induced suppression of inhibition was not altered in posttraumatic mossy cells. These data demonstrate that many intrinsic and synaptic properties of mossy cells undergo highly specific, long-term alterations after traumatic brain injury. The systematic nature of such extensive and opposing alterations suggests that single-cell properties are significantly influenced by homeostatic mechanisms in hyperexcitable circuits.

Topics: Animals; Animals, Newborn; Computer Simulation; Craniocerebral Trauma; Disease Models, Animal; Dose-Response Relationship, Radiation; Drug Interactions; Electric Stimulation; In Vitro Techniques; Membrane Potentials; Models, Neurological; Mossy Fibers, Hippocampal; Nerve Net; Neurons; Patch-Clamp Techniques; Piperidines; Potassium Channel Blockers; Pyrazoles; Pyrimidines; Rats; Sodium Channel Blockers; Tetraethylammonium; Tetrodotoxin

In order to clarify the effect of trauma and treatment as stresses on myocardia, we examined histological changes of myocardia in victims who received various kinds of traumata and treatments. We also undertook a histochemical study for calmodulin, which we found useful in the diagnosis of early ischemia. Those who died shortly after stab wounds, traffic accident or head injuries, showed mild cardiac lesions such as contraction bands or fragmentation and mild diffusion of calmodulin, a marker for necrosis. A case with hemorrhagic shock after a traffic accident, involving intense resuscitation for 2 h, showed severe cardiac lesions such as contraction bands, hydropic change and subendocardial hemorrhage along with severe diffusion of calmodulin. In most of the instant death cases after falls, severe contraction band necrosis and severe calmodulin diffusion were observed. Myocardia of victims, who died several days after head injuries or traffic accidents, generally demonstrated distinct diffusion of calmodulin as compared to the mild and non-specific lesions detected by hematoxylin-eosin (H&E) staining. In cases of long-term survival in a state of brain death, calmodulin staining was very low, which was not always associated with the severity of the lesions on H&E staining. In cases with intensive or extended treatment, it appeared to be difficult to determine the cause-effect relationship between trauma and cardiac lesions or to distinguish the lesions due to extrinsic factors from those of disease. In some cases, calmodulin intensely stained the areas with hydropic appearance or hypereosinophilia, which may be related to calcium overload.

Topics: Accidents, Traffic; Adolescent; Adult; Asphyxia; Brain Death; Calmodulin; Cause of Death; Craniocerebral Trauma; Death, Sudden, Cardiac; Female; Histocytochemistry; Humans; Immunoenzyme Techniques; Male; Myocardium; Resuscitation; Shock, Hemorrhagic; Tetrodotoxin; Wounds and Injuries; Wounds, Gunshot