UP-REGULATION OF INTERCELLULAR-ADHESION MOLECULE-1 IN CEREBRAL MICROVESSELS AFTER CORTICAL CONTUSION TRAUMA IN A RAT MODEL

A study was made on the expression of the intercellular adhesion molec ule 1 (ICAM-1) in cerebral microvessels after cortical contusion traum a of the rat brain. The trauma was produced by a free-falling weight o n the exposed dura of one fronto-parietal lobe. Immunohistochemistry w as done on cryostat sections using a monoclonal antibody and the react ion product was visualized using the avidin-biotin-peroxidase complex method. Control and sham-operated rats showed immunostaining of some p enetrating arteries of the cerebral cortex, the epithelial cells of th e choroid plexus and occasional microvessels of the brain parenchyma. The same pattern of immunostaining was seen in rats that were subjecte d to trauma and killed after 30 min. All rats with contusion trauma th at were allowed to survive for 6-72 h showed a substantial increase in the number of immunostained capillaries throughout the site of the le sion. The ipsilateral hippocampus showed a mild to moderate increase i n the number of immunostained microvascular profiles. This phenomenon was also present in the lateral thalamus of some rats. The staining wa s seen as an uninterrupted line at the position of the endothelial cel ls, indicating an upregulation of this adhesion molecule after brain t rauma. Up-regulation of ICAM-1 is a well-known phenomenon in inflammat ory and ischemic lesions of the brain but has not previously been desc ribed in detail in traumatic brain injury. ICAM-1 may be involved in t he production of several post-traumatic events such as leukocyte adhes ion, microcirculatory disturbances and edema formation.