The availability of a radiopharmaceutical able to measure 5-HT1A agonist sites, enables the undertaking of different protocols to explore 5-HT1A receptors in schizophrenia: either using [18F]-F13640 alone, or by comparing the labelling of [18F]-F13640 with that of [18F]-MPPF or [11C]-WAY1006365. Here, HTR1A is linked to schizophrenia.