Regulation of peripheral inflammation by the central nervous system.

In inflammatory disorders such as rheumatoid arthritis, cytokines and danger signals are sensed by the central nervous system, which adapts behavior and physiologic responses during systemic stress. The central nervous system can also signal the periphery to modulate inflammation through efferent hormonal and neuronal pathways. The brain and spinal cord are involved in this bidirectional interaction. A variety of neuronal pathways that modulate synovial inflammation have been implicated, including the sympathetic and the parasympathetic branches of the autonomic system. Another mechanism, the dorsal root reflex, involves antidromic signaling along somatic afferent fibers that influences joint inflammation by releasing neuropeptides and other neuromediators in the periphery. Some of the neurotransmitters and neuroreceptors involved have been identified in preclinical models and represent novel targets for the treatment of rheumatic diseases.