MAGNETIC-RESONANCE-IMAGING OF RAT-BRAIN FOLLOWING INVIVO DISRUPTION OF THE CEREBRAL VASCULATURE

Intravenous administration of hyperosmotic mannitol into rats produced a disruption of the blood-brain barrier (BBB). This was visualized by T1 weighted magnetic resonance (MR) imaging following intravenous administration of the MR contrast agent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Following administration of the Gd-DTPA there was an increase in signal intensity corresponding to the cerbral cortex. There was also an increase in signal intensity in features corresponding to the lateral ventricles. However, there was no increase in signal intensity within the striatum indicating that the vasculature within the striatum was resistant to disruption by the hyperosmotic mannitol. The tumors formed by C-6 glioma cells were isointense with rat brain on precontrast MR images. Following intravenous administration of Gd-DTPA, in a representative rat, the tumor was visualized as areas of high signal intensity. There was no enhancement of normal brain by Gd-DTPA. Thus, the tumor had different vascular properties than the host brain with respect to permeability of the contrast agent. Furthermore, Gd-DTPA did not enter the normal brain via the tumor. Thirty days following unilateral injection of kainic acid (KA:5 nmol) into rat striatum, the shrinkage of the lesioned striatum and the concomitant enlargement of the lateral ventricles was visible on the precontrast MR images. Following administration of Gd-DTPA, there was no enhancement of any regions of the brain. Therefore, the structural perturbations of the striatum produced by KA lesions were not accompanied by disruption of the BBB. These studies demonstrate that MR imaging represents a useful technique for investigating in vivo the perturbation of the cerebral vasculature in rat models of neuropathologies.