Depending on the individual pathology, a variety of the factors are involved in altering BBB permeability. Several groups of mediators appear to have a prominent role in BBB disruption. These include a group of vasogenic agents including histamine.
During the intra‐osseous phase of tooth eruption, the proportional increase in the number of mast cells in the lamina propria and osteoclasts indicates that mast cells could be involved in the bone resorption and, thereby, in the establishment of the eruptive pathway. Activated mast cells degranulate and thereby release several inflammatory mediators and growth factors, including histamine, cytokines such as tumour necrosis factor‐α (TNF‐α), vascular endothelial growth factor (VEGF) and various specific proteases.
Histamine is one of the few central nervous system neurotransmitters found to cause consistent blood-brain barrier opening. The earlier literature was unclear, but studies of pial vessels and cultured endothelium reveal increased permeability mediated by H2 receptors and elevation of [Ca2+]i and an H1 receptor-mediated reduction in permeability coupled to an elevation of cAMP.