Diurnal variations of interleukin-1 beta mRNA and beta-actin mRNA in rat brain.

Interleukin-1 beta (IL-1 beta) is posited to play an important physiological role in brain functions in addition to its better defined role in pathology. The experiments described herein were performed to determine if IL-1 beta mRNA and beta-actin display diurnal rhythms in various areas of brain. Rats were sacrificed at 4 h intervals across a 12:12 h light/dark cycle. Hypothalamic, hippocampal and cortical IL-1 beta mRNA peaked just after lights were turned on, declined slightly during the remaining light period and stayed low in the dark. There were no significant changes in IL-1 beta mRNA in brain stem or cerebellum samples. beta-actin mRNA levels were relatively constant across the day in the hypothalamus, brain stem and cerebellum. However, beta-actin mRNA levels were lower during the day than during the night in the hippocampus and cortex.