• Corpus ID: 92729925

Effects of transcranial light on molecules regulating circadian rhythm

@inproceedings{Flyktman2018EffectsOT,
  title={Effects of transcranial light on molecules regulating circadian rhythm},
  author={Antti Flyktman},
  year={2018}
}

• A. Flyktman
• Published 2018
• Biology

Light acts as the most important regulating and entraining factor of the mammalian circadian rhythm. This rhythm has evolved to set phases, in which different physiological and behavioral events occur at the right time of the day to synchronize the organism. The mechanism of light transduction via eyes to the brain and its effects on circadian rhythmicity is well known. Yet, it has also been shown that light is able to penetrate the skull bone directly, but it is still unknown, whether transcranial light is able to affect molecules regulating circadian rhythmicity. Monoamines and especially opsins have been shown to act as important regulators in circadian rhythmicity. Both group of molecules can mediate the effects of light on regulation and entrainment. In this thesis, mice and hamsters have been illuminated transcranially and the expression of three different opsins and the concentrations of several monoamines have been measured. The animals were illuminated under anesthesia either just after the onset of the light period or just after the beginning of the dark period. The opsin expression in rodent brain were measured by western blot and the monoamine concentrations from mouse brain, plasma and adrenal gland were measured by HPLC. It was observed that both opsin expression and monoamine concentrations can be influenced by transcranial illumination. The effect varied depending on the studied molecule, tissue and time of illumination. The findings of this study demonstrate that opsins, which are considered to be the most important molecules regulating circadian rhythmicity, can be directly and specifically affected not only via the eyes but also by light illuminated through the skull. Furthermore, monoamine production can be altered in both the central nervous system and the peripheral tissues by transcranial illumination. This thesis demonstrates an alternate pathway for circadian entrainment and regulation by light involving specific molecular mediators such as opsins and monoamines.