Diurnal variations of tumor necrosis factor alpha mrna and alpha-tubulin mRNA in rat brain

The experiments described herein were designed to determine whether tumor necrosis factor α (TNF-α) displays a diurnal variation in various areas of the normal rat brain. TNF-α mRNA transcripts were detected by reverse-transcriptase polymerase chain reaction. To monitor diurnal changes in TNF-α and α-tubulin expression, rats were sacrificed every 4 h for 24 h starting 1 h after light onset; relative mRNA levels were determined for the cerebellum, cortex, hippocampus, hypothalamus and brainstem. TNF-α mRNA was higher during the light than in the dark phase in the hypothalamus and hippocampus. α-Tubulin mRNA exhibited a similar diurnal variation in the hypothalamus, hippocampus and cortex. In contrast, (β-actin mRNA was lower during the light phase than the dark phase in the hippocampus and cortex. The observed diurnal variations in TNF-α mRNA are consistent with the hypothesis that TNF has a physiological role in the brain.