Two studies in migraine patients have further analysed plasma levels of markers of peptide release from parasympathetic (VIP) and sensory (CGRP) perivascular nerve fibres; mast cell degranulation (tumour necrosis factor alpha and tryptase); neuronal damage, glial cell activation or leakage of the BBB (S100 calcium binding protein B and neuron-specific enolase); and hypothalamic activation (prolactin, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone and adrenocorticotropic hormone) after PACAP infusion [114, 118]. Here, VIP is linked to migraine disorder.