A couple of months ago I wrote about a study in primates, suggesting that there is a circadian clock in the adrenal gland. This was hyped like a big break-through, but, while that was a good and useful study, it did not show anything surprising, e.g., that the adrenal is a pacemaker, only that it is a peripheral clock, which was known for decades, before the whole paradigm of perihperal clocks matured within the field.
Now, there is a new study, this time in mice, on the same question: How the adrenal 'clock' keeps the body in synch.
Again, it is touted as something that will fundamentaly change the field:
The circadian network now revealed for the adrenal gland might serve as a "paradigm for the organization of other physiological rhythms," the researchers said. The findings might also require scientists to do some rethinking, Oster added. Previous studies using organ cultures found that clock gene rhythms can persist for weeks in the absence of external timing signals, leading to the suggestion that peripheral clocks to a large extent operate independently. In marked contrast, the loss of corticosterone rhythm in clock mutant animals with normal adrenals after 2 days in constant darkness indicates a critical dependence of the adrenal on input from the master clock, Oster said.
The study is good, but there is nothing really new and earth-shattering.
We knew there was a peripheral clock in the adrenal.
We knew that peripheral clocks are autonomous in a dish.
We knew that peripheral clocks get entrained/synchronized by neural and/or hormonal inputs from the central pacemaker (e.g., the SCN in mammals).
We knew that peripheral clocks feed back onto the pacamaker.
We knew that every clock has its own rhythm of sensitivity to its entraining agents (e.g., light, food, hormones, neurotransmitters) - that is why we make Phase-Response Curves.
So, we knew that each clock "gates" its own responses to synchronizers - that is the reigning paradigm in the field, not something new that will have to come out of this particular study.
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