MAGNETIC-RESONANCE-IMAGING OF TEMPORAL CHANGES OF NEUROTOXIC LESION IN THE RAT

Destruction of striatal neurons in the rat brain, induced by intracere bral injection of N-methyl D-aspartic acid (NMDA), has been visualized noninvasively by magnetic resonance imaging (MRI). The changes in ima ges were monitored from 12 h to one month after the stereotaxic microi nfusion of NMDA (10 mu g in 0.4 mu l) into the striatum, using a T-2-w eighted rapid acquisition by relaxation enhancement (RARE) sequence, A localised hyperintense (bright) area was visible after 12 h at the si te of the injection, and it persisted for the next three days. The siz e of the hyperintense area decreased thereafter and, after one week, t he increased brightness was restricted to the lateral ventricle. Post- mortem histological examination, done after one month, showed a dilate d lateral ventricle. The size and location of the lesioned area, ident ified in histological sections, corresponded to the hyperintense area observed during these initial days after NMDA lesion. The present stud y demonstrates that noninvasive MRI techniques, using a typical RARE s equence, offer a powerful tool for the early detection of neurotoxic l esion of the brain area, although some caution is required in its use for estimating the size of the lesioned area three days after its form ation. The present findings indicate that, in long-term studies, alter ations of the neighbouring structures, such as enlargement of the vent ricular system, may confound the MRI evaluation of neurotoxic lesions in vivo.