Search for Seasonal Rhythmicity of Pineal Melatonin Production in Rats Under Constant Laboratory Conditions: Spectral Chronobiological Analysis, and Relation to Solar and Geomagnetic Variables

Abstract

Earlier we reported that in a number of experiments pineal melatonin production in rats under constant laboratory conditions displayed seasonal rhythms but subsequently were not always able to confirm this. Since there was no indication under which conditions such rhythms may be present, we performed four consecutive identical experiments with untreated female Sprague-Dawley rats within the same animal room during 1997-2006. Nocturnal urine samples (19-23, 23-3, 3-7 h) were collected at monthly intervals over 494-658 d with 12 animals each in experiments I and II (1997-1999, 1999-2000), 30 animals in experiment III (2002-2004), and 15 in experiment IV (2005-2006). 6-Sulfatoxymelatonin (aMT6s) was measured by ELISA. The excreted aMT6s at each time interval as well as total nocturnal aMT6s-excretion (19-7 h) was submitted to standard statistical analyses as well as to a spectral chronobiological analysis to determine the period lengths of the components involved which was followed by processing with the single cosinor method. Seasonal rhythm components (circannual period length: 360 ± 60 d) were detected in experiment III (2002-2004) for the overall nocturnal excretion as well as for two sub-intervals (23-3 and 3-7 h) and in one night interval of experiment II (23-3 h). Multiple components with mostly short period lengths of around 100 d and some long ones of 500-650 d were found in the other experiments. Systematic MESOR and amplitude variations were observed during the experiments, being highest in experiment II (19-7 h, also 23-3 h and 3-7 h) and lowest in experiments I and IV. These results illustrate that seasonal melatonin rhythms are not a general phenomenon in female laboratory rats indicating an involvement of unknown environmental cues. As an extension of our earlier hypothesis regarding a seasonal Zeitgeber function of the horizontal intensity H of the geomagnetic field showing circannual variations, we assume further modulation by the 11-yrs' sunspot cycle which leads to geomagnetic disturbances and could facilitate seasonal aMT6s rhythmicity during specific years.

Time related variations in stem cell harvesting of umbilical cord blood

“…These results highlight a possible involvement of non-photic cues and give hypothetical support to a seasonal Zeitgeber function of the horizontal intensity H of the geomagnetic field that shows circannual variations. Additionally, the 11-years’ sunspot cycle also drives geomagnetic disturbances and could facilitate seasonal 6-sulfatoxymelatonin rhythmicity during specific years 54 55 . Interestingly, in our study CBV showed a clear trough after the solar maximum (1999–2002), at a time when geomagnetic disturbances were maximal during the last solar cycle.…”

Effect of occupational EMF exposure from radar at two different frequency bands on plasma melatonin and serotonin levels

“…Moreover, the participants belonged to the same occupational group and military setup, their lifestyle, diet, and exercise protocols were the same with similar physical characteristics. Further, the studies by Bartsch et al (1994Bartsch et al ( , 2010Bartsch et al ( , 2012aBartsch et al ( , 2012b have indicated the possible influence of the natural environment with respect to changes in solar activity through the 11-years sunspot cycle which, might cause geomagnetic disturbances by altering the direction and intensity of the horizontal magnetic field component and thereby controlling the upshots of man-made EMF experiences on health, survival and melatonin rhythm as well. The authors have therefore stressed the importance of year and season in endocrine research regardless of the homogenous environmental conditions negligence of which Int J Radiat Biol Downloaded from informahealthcare.com by Gazi Univ.…”

Seasonal postembryonic maturation of the diurnal rhythm of serotonin in the chicken pineal gland

“…Experiments conducted on female laboratory rats over a 2-year-period indicated that the urinary excretion of 6-sulfatoxymelatonin (aMT6s) displays a seasonal rhythm and it was hypothesized that this rhythm is related to the geomagnetic field, which may act as a seasonal zeitgeber (Bartsch et al, 2012a). These authors suggested that the 11-year-sunspot cycle causes geomagnetic disturbances that probably facilitate seasonal aMT6s rhythmicity (Bartsch et al, 2012b).…”