Drastic increase in nitric oxide content in rat brain under halothane anesthesia revealed by EPR method

A drastic increase in nitric oxide (NO) content was revealed by the EPR met hod in rat brain cortex and cerebellum under halothane anesthesia. The NO s cavenger diethyldithiocarbamate sodium salt (DETC) and ferrous citrate were injected into adult rats 30-60 min before anesthesia. Rats were anesthetiz ed by inhalation of a halothane-oxygen mixture (1%, 1.5%, 2%, or 4%). After different times of anesthesia, rats were decapitated, and brain cortex and cerebellum were dissected, frozen in liquid nitrogen, and subjected to EPR spectroscopy. The concentration of NO was determined from the NO-Fe-DETC r adical spectrum. In control animals, NO content in the cerebellum was only 68% of that in the cortex. We observed a rime-dependent increase in NO cont ent in the cortex and cerebellum of rats anesthetized with 1.5% halothane. In brain cortex, the NO level increased to six times that of waking animals after 30 min and remained at this level up to 60 min of anesthesia. In cer ebellum the changes were less drastic, the NO level showing only a 2-fold i ncrease. The same effect was produced by 1% and 2% halothane. Ketamine, chl oral hydrate, and pentobarbital were used as reference drugs. None of these anesthetics produced effects similar to those of halothane. In ketamine-an esthetized rat brain, the NO content slightly decreased. Pentobarbital and chloral hydrate produced an insignificant increase in NO. Data are discusse d in the context of possible interference of halothane in the regulation of nitric oxide synthase activity. (C) 1999 Elsevier Science Inc.