Because their exact role in the microbiota–gut–brain axis has not yet been clarified, neuropeptides, such as alpha-melanocyte-stimulating hormone (α-MSH), beta-endorphin (β-End), neurotensin (NT), and substance P (SP), must be screened in different rodent models of ASD as neurodevelopmental disorders with GI co-morbidity. This evidence concerns the gene POMC and neurodevelopmental disorder.