Molecules involved in stress-related disorders and in response to physical activity, such as glutamate, cAMP, glucocorticoids, oestrogen, and pro-inflammatory cytokines, can alter the expression of the prominent BBB tight junction protein claudin-5 either by direct or indirect mechanisms, resulting in a change in the BBB permeability with direct effects on the neuronal function, reviewed in [152]. The gene discussed is CLDN5; the disease is stress-related disorder.