Chronobiology international
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In birds, independent circadian clocks reside in the retina, pineal, and hypothalamus, which interact with each other and produce circadian time at the functional level. However, less is known of the molecular clockwork, and of the integration between central and peripheral clocks in birds. The present study investigated this, by monitoring the timed expression of five core clock genes (Per2. ⋯ For example, both rbCry2 and rbClock peaks were close to rbCry1 and rbBmal1 peaks, respectively, in the hypothalamus, but not in other tissues. The results are consistent with the autoregulatory circadian feedback loop, and indicate a conserved tissue-level circadian time generation in buntings. Variable phase relationships between gene pairs forming positive and negative limbs of the feedback loop may suggest the tissue-specific contribution of individual core circadian genes in the circadian time generation.