SOD1G93A mice are a transgenic model of Amyotrophic lateral<br>sclerosis (ALS) to investigate in vivo neuroinflammation with innovative<br>translocator protein radioligands and positron emission<br>tomography (PET). The possibility to perform serial studies in the<br>same animal, from the asymptomatic to the advanced stages, is<br>highly desirable. Alterations of nutrition, hydration and of cardiovascular<br>hemodynamics provide challenges for researchers and<br>can adversely affect imaging studies. 10 hemyzigous SOD1G93A<br>mice (aged 71-137 days) were evaluated at different clinical stages<br>(CS, score range: 0-4) by [18F]DPA-714 PET/CT (GE Healthcare<br>eXplore Vista, resolution: 1.8 mm FWHM/200 μm). 5 mice were<br>longitudinally monitored. Weight, body condition (BCS, 0-5) and<br>dehydration were daily monitored. From CS and BCS scored as 2,<br>palatable source of hydration and energy were left on cage floor.<br>Glucose 5% /Ringer lactate or NaCl 0.9% solutions (1-3 ml/day)<br>with multivitaminic supplement were provided parenterally.<br>Mice were housed in dry cage with soft bed, avoiding social<br>isolation. Ocular discharges and ulcerative lesions were cleaned<br>(NaCl 0.9%; iodopovidone). Imaging studies were performed<br>under inhalant anesthesia (isoflurane 2% and oxygen 2 L/min).<br>Radiotracer uptake (SUV) was measured on PET/CT fusion images<br>in the cerebellum, brainstem, spinal cord normalized to those<br>of the frontal cortex using Osirix software. In the single PET/CT<br>group, 3 mice died after imaging study (CS: 1-2; BCS 3; weight<br>gain +2.87g), while 2 mice were euthanized after 6 days (CS: 4;<br>BCS 2; weight loss -3.04g). Mice performed from 2 to 5 imaging<br>sessions, with a mean survival of 6 days after the last PET/CT<br>(CS: 2-4; BCS 2-3; weight loss -1.68g). SUV showed an increased<br>trend overtime in brainstem compared to age-matched controls.<br>These findings underlie the relevant role played by the special<br>care of transgenic murine models in order to improve longitudinal<br>studies and minimize confounding variables.<br>The research leading to these results has received funding from the<br>European Union’s Seventh Framework Programme (FP7/2007-2013)<br>under grant agreement n° HEALTH-F2-2011-278850 (INMiND).