The Pineal Gland and Chronobiologic History: Mind and Spirit as Feedsidewards in Time Structures for Prehabilitation

Abstract

Not only circadian rhythms — recurring patterns with a period of about 24 h (in the range of 20-28 h) — but also ultradian and infradian rhythms (with periods shorter than 20 h and longer than 28 h, respectively), characterize melatonin in humans, whether it is measured in blood, saliva, or urine. Among infradians, the about-yearly (circannual) and half-yearly (circasemiannual) components are noteworthy. At mid-latitude, circannuals may predominate in circulating melatonin during the daytime, whereas circasemiannuals may become more prominent during the nighttime. A stable half-yearly component also prominently characterizes the geomagnetic disturbance index Kp. Support for the hypothesis that Kp may influence human melatonin is provided by the fact that closer to tine pole, at 65 °N in Oulu, Finland, geomagnetic effects are stronger. There, circulating melatonin, measured around noon, exhibits a clear circasemiannual variation. Circaseptans and circasemiseptans, with periods of about a week and half a week, are found ubiquitously in relation to the pineal gland. In the case of melatonin secreted into the superfusion fluid by the pike pineal in vitro, kept at constant temperature in continuous darkness, the circaseptan component has an amplitude larger than that of the circadian rhythm. Circaseptans are also observed in the mouse pineal gland in vivo, wherein the presence of melatonin has been questioned, yet established by three independent groups of investigators who all documented a circadian variation peaking during the dark (rest) span.