Indeed, several studies are investigating MAO-B levels as a potential marker of astrocytic reactivity using positron emission tomography technique in conditions such as traumatic brain injury, major depressive disorder, post-traumatic stress disorder, and alcohol use disorder, employing the radiotracer [11C]SL25.1188 [47,48,49,50], but also Alzheimer’s disease, using [18F]SMBT-1 [51]. The gene discussed is MAOB; the disease is major depressive disorder.