Evaluation of Myelin Radiotracers in the Lysolecithin Rat Model of Focal Demyelination: Beware of Pitfalls!

International audienceThe observation that amyloid radiotracers developed for Alzheimer's disease bind to cerebral white matter paved the road to nuclear imaging of myelin in multiple sclerosis. e lysolecithin (lysophosphatidylcholine (LPC)) rat model of demyelination proved useful in evaluating and comparing candidate radiotracers to target myelin. Focal demyelination following stereotaxic LPC injection is larger than lesions observed in experimental autoimmune encephalitis models and is followed by spontaneous progressive remyelination. Moreover, the contralateral hemisphere may serve as an internal control in a given animal. However, demyelination can be accompanied by concurrent focal necrosis and/or adjacent ventricle dilation. e in uence of these side e ects on imaging ndings has never been carefully assessed. e present study describes an optimization of the LPC model and highlights the use of MRI for controlling the variability and pitfalls of the model. e prototypical amyloid radiotracer [ 11 C]PIB was used to show that in vivo PET does not provide su cient sensitivity to reliably track myelin changes and may be sensitive to LPC side e ects instead of demyelination as such. Ex vivo autoradiography with a uorine radiotracer should be preferred, to adequately evaluate and compare radiotracers for the assessment of myelin content