Nitric oxide in cerebrospinal fluid and local inducible nitric oxide synthase after cauda equina compression in rats.

We investigated the time course of changes in nitric oxide metabolite (NO2- plus NO3-: NOx) levels in the cerebrospinal fluid and the expression of local inducible nitric oxide synthase following cauda equina compression in rats. Cerebrospinal fluid NOx levels were significantly increased from 12 h to 3 days after compression, and decreased thereafter. Histologically, inducible nitric oxide synthase immunoreactivity was observed in macrophages that infiltrated the dura mater on days 1 and 3 after compression, but not in foamy macrophages in the parenchyma of the cauda equina observed afterwards. The pattern of NOx levels coincided with the appearance of inducible nitric oxide synthase labeled macrophages, indicating a critical role of these cells as the main synthesizers of NOx in the acute stage of cauda equina compression.