A bidirectional relationship links the immune and nervous systems, which communicate through the synthesis and the release of mediators such as cytokines, prostanoids, neuropeptides, and neurotransmitters. CRH: corticotropin-releasing hormone. CRF: corticotropin-releasing factor. ACTH: adrenocorticotropic hormone. NTS: nuclei of the solitary tract. LC: locus coeruleus. SNS: sympathetic nervous system. PNS: parasympathetic nervous system.