<P> Molecules called pro-inflammatory cytokines, which include interleukin - 1 (IL - 1), Interleukin - 2 (IL - 2), interleukin - 6 (IL - 6), Interleukin - 12 (IL - 12), Interferon - gamma (IFN - Gamma) and tumor necrosis factor alpha (TNF - alpha) can affect brain growth as well as neuronal function . Circulating immune cells such as macrophages, as well as glial cells (microglia and astrocytes) secrete these molecules . Cytokine regulation of hypothalamic function is an active area of research for the treatment of anxiety - related disorders . </P> <P> Cytokines mediate and control immune and inflammatory responses . Complex interactions exist between cytokines, inflammation and the adaptive responses in maintaining homeostasis . Like the stress response, the inflammatory reaction is crucial for survival . Systemic inflammatory reaction results in stimulation of four major programs: </P> <Ul> <Li> the acute - phase reaction </Li> <Li> sickness behavior </Li> <Li> the pain program </Li> <Li> the stress response </Li> </Ul> <Li> the acute - phase reaction </Li>

The chemical brain transmits which percentage of communication within the pni system