THE ONTOGENY OF A NEUROTOXIC LESION IN RAT-BRAIN REVEALED BY COMBINEDMRI AND HISTOLOGY

We have used magnetic resonance imaging (MRI) of the Living rat brain to longitudinally analyze the ontogenesis of an ibotenic acid lesion t argeted at the piriform cortex. The MRI data were systematically compa red with data obtained from a battery of histopathological techniques, including Nissl stain, hematoxylin stain, and a stain for cytochrome oxidase activity. Two days after the lesioning, widespread and heterog eneous damage mas detected in, around and distant from the toxin-targe ted area. Some damage apparently diminished within approximately 10 da ys, whereas other damage remained throughout the length of this study (60 days). We found that the small-animal MRI technology used by us is useful in determining the initial, transient impact of surgery and ne urotoxic lesioning, and in delineating the gross effects of the lesion over time. This is particularly useful for early elimination of anima ls from the protocol of physiological and behavioral experiments in wh ich the lesion exceeds the target area. Our data also indicate that, i n order to avoid confounding effects of transient post-lesioning pheno mena, behavioral and physiological tests should be carried out in neur otoxically lesioned animals >2 weeks after infliction of the lesion.