Noxious stimulation enhances release of cytokine-induced neutrophil chemoattractant from hypothalamic neurosecretory cells.

Cytokine-induced neutrophil chemoattractant (CINC), a member of IL-8 family in rat and a counter part of human growth-related oncogene product (GRO), was demonstrated to be synthesized in hypothalamic neurons and released in peripheral blood in response to noxious stimulation. CINC immunoreactive neurons were found mainly in supraoptic nucleus, while positive fibers were found in the median eminence and the posterior lobe of pituitary gland. Colchicine injection into the third ventricle demonstrated additional CINC positive neurons in both parvo- and magno-cellular parts of paraventricular nucleus, and an increase of positive fibers in the external layer of the median eminence. After formalin injection into the foot pad, CINC immunoreactivity substantially increased in the posterior lobe of the pituitary gland and in the external layers of the median eminence. In addition, a parallel increase of CINC level was noticed in the peripheral blood. It is suggested from the present results that, in response to a noxious stimulation, CINC is released from hypothalamic neurosecretory cells via both the anterior and posterior pituitary system. This cytokine mediated noxious response from CNS to peripheral tissue, would be a novel type of cross-talk between nervous and immune system.