Chronobiologic lead study cost-effectively assesses circadian-circaseptan intermodulation in murine pineal melatonin content.

The investment into the design of a study is usually and unfortunately proportional to the available information, i.e. the less one knows the more one is tempted to skimp and perform a minimal 'pilot' study. This is particularly true with respect to chronobiology. On the contrary, at the outset of a study, when the information available regarding a given problem is minimal or zero, the investment into a first study should be near-maximal. Accordingly, the often wasted 'pilot study' should be replaced by a rigorous chronobiologic lead study. The promise of such a chronobiologic 'guide, leading along a difficult or unknown course' is illustrated by the validation with statistical significance of an about-weekly (circaseptan) and an about 24-h (circadian) rhythm in the melatonin content of the murine pineal. Work around the clock on 48 female Lewis/S rats was avoided. Replication of 6 different circadian times on different comparable animals on consecutive days assessed a circaseptan rhythm more prominent than the concomitantly demonstrated circadian, at no added cost for experimental animals beyond those often used for circadian study and with no work around the clock.