Biological processes are optimized by circadian and circannual biological timing systems. In vertebrates, the pineal gland plays an essential role in these systems by converting time into a hormonal signal, melatonin; in all vertebrates, circulating melatonin is elevated at night, independent of lifestyle. At night, sympathetic input to the pineal gland, originating from the circadian clock in the suprachiasmatic nucleus, releases norepinephrine. This adrenergic stimulation causes an elevation of cAMP, which is thought to regulate many of the dramatic changes in genes expression known to occur at night. In many aspects, the adrenergic/cAMP effects on gene expression can be recapitulated in primary organ culture.
We have analyzed the rat pineal transcriptome at mid-day and mid-night to identify genes that exhibit night/day changes in expression. The pineal transcriptome was compared to that of other rat tissues processed in parallel. In addition, pineal glands were cultured in control conditions, or stimulated with norepinephrine, dibutyryl-cAMP (DBcAMP), or forskolin; the transcriptomes of these glands were then analyzed.
Keywords: Time course (2 points) for in vivo pineal glands and various tissues; Treatment groups for cultured pineal glands
Overall design: Total RNA was extracted from various rat tissues, and from both in vivo and cultured rat pineal glands, for processing and hybridization to Affymetrix microarrays. Quadruplicates of pooled in vivo pineal glands were analyzed at each timepoint. Single day and night samples of retina, cortex, cerebellum, hypothalamus, liver, and heart were analyzed. Triplicates of control and treated cultured pineal glands were analyzed.
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