Neuronal free Ca2+and BBB permeability and ultrastructure in head injury with secondary insult

Abstract

Objective: To study changes in free calcium (Ca2+), neuronal and blood–brain barrier (BBB) permeability and ultrastructure in brain after diffuse axonal injury (DAI) with secondary brain insults (SBIs).Method: One hundred and twenty Sprague-Dawley (SD) rats were randomised into control, DAI alone and DAI with SBI groups which were sub-divided into 5 groups that were 0.5h, 2h, 12h, 24h, 48h post trauma. The animal models of DAI and DAI with SBI have been described before (2). Fluorescence probe Fluo-3/Am was used to measure free Ca2+in neurons. Laser scan microscopy was used to detect fluorescence intensity. After the animals were anesthetized, Lanthanum nitrate liquid was used for intracardiac perfusion to assess BBB permeability. Under the transmission electron microscope, changes in cerebral ultrastructure and BBB permeability were observed.Results: The fluorescence intensity was weak in the control. The concentration of free Ca2+in neurons was obviously increased at 30 min after brain injury, reached a peak at 12h–24h (P< 0.01), and appeared to decrease at 48h after injury. In the DAI alone group, BBB tight junction opening with particles of Lanthanum nitrate outside the vessels was found at 30min after injury, and peaked at 24h. In DAI with SBI, the changes in ultrastructure and BBB permeability were more severe than that in the DAI alone group at the same time interval. The shape of the fluorescence concentration curve was basically the same for both kinds of brain injury. The intensity of fluorescence in DAI with SBI was higher than that in the DAI alone group at the same time interval (P< 0.05).Conclusion: In DAI alone and DAI with SBI, Ca2+overload and BBB permeability changes interact and both play important roles in the aggravation of brain damage.