De plus, l’imagerie moléculaire permet la détection de modifications fonctionnelles précédant la pathologie manifeste, ce qui est particulièrement utile pour le diagnostic précoce et le traitement des troubles du SNC. Dans cet article, nous nous intéressons à la capacité de l’imagerie moléculaire d’informer sur le développement et l’évaluation des traitements dans son application aux troubles du SNC, en particulier pour la schizophrénie, la maladie de Parkinson, la dépression et la démence, troubles majeurs du SNC. Nous analysons également la possibilité de piloter le développement de nouveaux médicaments

des troubles du SNC par l’imagerie moléculaire. Introduction Molecular Inhibitors,research,lifescience,medical imaging techniques Inhibitors,research,lifescience,medical such as positron emission

tomography (PET) and single photon emission computed tomography (SPECT) enable the in vivo characterization and measurement of biologic processes using high-affinity and high-specificity molecular probes.1 PET and SPECT use molecules labeled with a radionuclide that emits photons, known as a radiotracer or radioligand, that are detected in the scanner to provide data on the localization of the radiolabeled molecule in the tissue of interest. As such they provide a noninvasive means of visualizing, and characterizing physiological processes in vivo and the opportunity to make discoveries in the living, intact Inhibitors,research,lifescience,medical brain. The major

differences between PET and SPECT stem from the such information nature of the radionuclides used to label the tracer. The most commonly used radionuclides are 99mTc, 111In, 123I and 201T1 for SPECT, and 11C, 13N, 15O, and 18F for PET. The radionuclides used for SPECT have relatively long half-lives, in Inhibitors,research,lifescience,medical the range of hours, and emit a single photon. In contrast, those used in PET have Inhibitors,research,lifescience,medical shorter half-lives, in the range of minutes to just under 2 hours in the case of 18F, and emit a positron, which annihilates when it collides with nearby electrons to emit two photons. The difference in the nature Brefeldin_A of photon emission leads to differences in emission detectors and image construction — SPECT uses collimation and PET uses coincidence detection. The advantages and limitations of both techniques follow from these properties — as SPECT tracers have longer half-lives they do not need an on-site cyclotron and, multiple scans are possible from one synthesis; this means they are cheaper to make than PET tracers. protein inhibitor However, PET uses radionuclides that tend to be easily combined with biological molecules, and has better resolution. Imaging in vivo can avoid the various potential biases or confounds of ex vivo studies, such as exposure to psychotropic drugs or mis-counting object fragments in a sectioned tissue volume2 whilst also enabling molecular alterations to be linked to clinical changes.