1. Comparative Analysis of Various
Circadian Rhythms
Ryan Freeland, James M. Mossner, Tiecheng Liu, M.D., Jimo Borjigin, Ph.D.
Department of Molecular & Integrative Physiology; University of Michigan Medical SchooL, Ann Arbor
(Fig 2.) Basic melatonin location and formation in the
brain.
1
(Fig. 7) A. F344
(Fig. 9) B. F344 (Fig. 10) C. F344
(Figs. 11 and 12) Images of the animals in our lab.
• Goal of the project:
o To compare and contrast four different methods of circadian rhythms, including (1) melatonin secretion from the pineal gland, (2) PIR, (3) telemetry, and (4) wheel running.
• James’ data conclusions (developed from JMM ppt SURP 2012):
o Two spikes of activity were found with PIR, telemetry measurement;
o The 1st spike is not found in melatonin rhythms;
o The 2nd spike is more closely related to the onset of melatonin secretion.
• My data conclusions:
o Preliminaries were unable to show a clear correlation between 1st and 2nd spike of activity and melatonin secretion;
o Possible implications: age of rat, rat’s surgery, cage obstructions, computer error.
• Future Directions:
o To repeat wheel running study in the same rats with melatonin data;
o To determine which activity method gives best circadian results;
o To determine the source of the 1st activity spike.
PIR vs. Melatonin
Telemetry-Temperature vs. Melatonin
James M. Mossner’s PIR vs. Melatonin
(Fig. 8) D. Data collected Summer 2012 from James M. Mossner’s SURP Fellowship.
Methods
6 Conclusions
Abstract
Our laboratory has established a chronic microdialysis-HPLC system to
measure the melatonin profile of freely moving rodents and is a unique tool of
our laboratory.
While it gives accurate melatonin secretion information, it is difficult to per-
form due to various reasons, including experiment cost and technically (surgi-
cally) challenging. In most circadian research laboratories around the world,
however, more common techniques are used to measure an organism’s activity.
These common techniques include passive infrared (PIR) sensors, wheel-run-
ning, and telemetry systems, of which the latter also measures temperature.
In order to ensure the accuracy of these activity measurement techniques, a
comparison to the melatonin profile, the best-known indicator of circadian
rhythms in both humans and animals, is essential. A comprehensive comparison
between the melatonin profile obtained using our techniques and activity pro-
files monitored using other techniques, however, has never been analyzed. The
data for the wheel-running system is still under experimentation. Our goal is to
indentify the common rhythmic features underlying all circadian rhythms by
comparing the similarities and differences of multiple parameters with that of
melatonin.
Circadian rhythms are endogenously driven cycles that are approximately 24 hours long.
These rhythms occur in almost every organism. Circadian rhythms are very important to the
human body because they assist in maintaining homeostatic conditions, such as metabolism,
hormone secretion, and sleep/wake cycles. In this study, we will be comparing several biomark-
ers (activity, temperature, and melatonin) to determine the underlying principle of all circadian
rhythms.
Melatonin is secreted by the pineal gland and is derivatived from the amino acid, trypto-
phan. Ultimately, melatonin modulates the central circadian clock, which is located in the su-
prachiasmatic nucleus (SCN) of the hypothalamus. Therefore, melatonin is the best indicator of
what is happening in the circadian clock, and serves as the “hands of the clock.”
(Fig. 4) PASSIVE-INFRA-
RED (PIR) SENSORS:
measures activity of animal
using infrared sensors.
(Fig. 6) WHEEL-RUNNING: Golden stan-
dard for activity measurements.
(Fig. 5) TELEMETRY: small device
that is surgically implanted in ab-
dominal cavity; provides tempera-
ture and activity.
(Fig. 3) HPLC-MICRODIALYSIS SYSTEM: measures
pineal melatonin levels in real time.
(Fig 1.) Circadian rhythm picture for a typical human.
Background Information Results2
Acknowledgements3
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5
James M. Mossner, Tiecheng Liu, M.D., Jimo Borjigin, Ph.D., Fedor Bayalev, Megan Hagenau-
er, Ph.D., James A. Mossner, Department of Molecular & Integrative Physiology, University of
Michigan Medical School
Telemetry-Activity vs. Melatonin