But even this apparently benign role may have a darker side as substance P immunoreactive astrocytes have been identified in MS plaques (Kostyk et al., 1989), and a requirement for substance P/NK-1R interactions has been reported for the maintenance of chronic inflammation in experimental autoimmune encephalomyelitis (EAE) mouse models of MS (Reinke et al., 2006). This evidence concerns the gene TAC1 and myeloid sarcoma.