Diurnal variation of TNFα in the rat brain

TUMOR necrosis factor-α (TNFα) is thought to play a physiological role in the brain. These studies were performed to determine whether a diurnal rhythm of TNFα exist in the rat brain. Samples were collected from hippocampus, hypothalamus, cerebral cortex, cerebellum, pons and midbrain at light onset and at 6 h intervals thereafter over a day. A TNFα bioassay was used to measure TNFα in each area. TNFα was highest at light onset in the hypothalamus, hippocampus and cerebral cortex. Levels at light onset were about 10-fold greater than minimal night-time levels. Changes in TNFα activity in other brain areas were also evident, but smaller. These results support the hypothesis that TNFα has physiological roles in the brain.