Using MRI to predict the fate of excitotoxic lesions in rats.

Thibault Cholvin,Nathalie Baril,Lisa Giorgi,Bruno Poucet,Franck A Chaillan,Jean-Michel Brezun

doi:10.1371/journal.pone.0200659

Abstract

Excitotoxic lesions are frequently used to assess the role of cerebral structures in cognitive processes in rodents. However, the precise site and extent of these lesions remain unknown without histological verifications. Using a 7-Teslas MRI system and a T2-weighted turbo-RARE sequence, MR images were acquired at several time points following NMDA lesions (1h, 6h, 24h, 48h, 1 week and 2 weeks). NMDA infusions into the parenchyma induced a clear and delineable hyperintense signal from 1h up to 1-week post-surgery. Hyperintensity volumes were compared with NeuN and Cresyl violet histological quantifications of the lesion magnitude. NMDA-induced hypersignal is observed as soon as 1h post-injection and is a reliable estimate of the presence (or absence) of a lesion. Compared to NeuN, Cresyl violet staining underestimates the extent of the lesion in significant proportions. The MRI hyperintensity generated by NMDA instillation into the parenchyma can be used as a powerful tool to confirm the diffusion of the drug into the cerebral tissue, to ascertain the locus of injection and predict with a high success rate the fate of NMDA lesions as soon as 1h post-surgery. This approach could be very useful in a large variety of lesion studies in rodents.

Highlights

Magnetic resonance imaging (MRI) is a powerful non-invasive tool to assess numerous brain afflictions in humans
MRI has especially been used in rodents to assess the evolution of tissue damage following traumatic brain injury [1,2], to detect and measure the size of lesions induced by focal cerebral ischemia [3] and to investigate the functional disruption in rat olfactory circuitry after radiofrequency lesion [4]
We found that NeuN staining is more reliable than cresyl violet staining, and that MRI scans made shortly after NMDA instillations are a good predictor of the final histological outcome as assessed with NeuN

Summary

Introduction

Magnetic resonance imaging (MRI) is a powerful non-invasive tool to assess numerous brain afflictions in humans. In animals, this approach could help experimenters precociously evaluate the success of the brain manipulations they intend to carry out, such as excitotoxic lesions. The early detection of ibotenic acid-induced lesions has been documented in monkeys [10,11]. Most of these studies used Cresyl violet for post-mortem histological examination [5,6,8]

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