HTR1A and treatment resistant depression: Based on this evidence, we aimed at assessing the impact of bilateral TBS on 5-HT1A receptor distribution in a sample of TRD patients using the radioligand [carbonyl-11C]WAY-100635 to probe the hypothesis of a 5-HT1A receptor reduction in the DLFPC – as seen with other antidepressant treatments – by this non-invasive brain stimulation technique in vivo.