Dr. Gianluca Tosini is studying the organization of the mammalian circadian system. Through this research, he will examine how the different components of the circadian system interact and how prolonged exposure to altered lighting conditions affects the system. The research will help foresee and prevent dysfunction of circadian rhythm in space and help understand the biological bases of sleep disturbance and some types of depression.
Overview
Long-Term Exposure to Dim Lighting Desynchronizes the Circadian System of Rats
Principal Investigator:
Gianluca Tosini, Ph.D.
Organization:
Morehouse School of Medicine
Technical Summary
Many biochemical, physiological and behavioral parameters exhibited by organisms show daily fluctuations and most of these daily rhythms persist in constant conditions, thus, demonstrating that they are driven by endogenous oscillators. The rhythms that persist in constant conditions with a period close to 24 hours are called circadian rhythms. One the most important aspects of space flight is the absence of geophysical 24-h cycles, which, of course, affects the overall temporal organization of the organisms. In the case of long-duration manned space flight, it is crucial to understand how the whole circadian system would react and behave in such circumstances.
We discovered that exposing rats to constant dim light for 60 days significantly affected the phase-relationship among circadian outputs in the SCN, retina and pineal, demonstrating that in these animals internal desynchronization of the circadian rhythms is occurring. We also observed that the circadian rhythm in arylalkylamine N-acetyltransferase (the enzyme that is responsible for the circadian rhythm in melatonin synthesis) was altered in both the retina and in the pineal gland. Our data also indicated that locomotor activity rhythm might be an unsatisfactory marker to assess the circadian status of the whole organism. Internal desynchronization has profound effects on the capability of the organisms to perform (mentally and physically) and to remain healthy. In this research proposal, we have designed a series of experiment aimed to understand the mechanisms that are responsible for the observed desynchronization. We believe that the model we have generated will be useful in to foreseeing and preventing dysfunction of the circadian system that may arise after long periods in the space environment where the normal cycle has been altered.
This project's funding ended in 2004