1. ARULMIGU KALASALINGAM COLLEGE OF PHARMACY
M.Arumugavignesh1, R.Vigneswaran1,
Dr. V. Lavakumar2†, Dr. N. Venkateshan3
1
Pharm D, second year Arulmigu Kalasalingam
College of Pharmacy, Anand Nagar,
Krishnankoil, Srivilliputtur – 626126, TN.
2
Drug Delivery and Nanotechnology
Laboratory(DDNL), Arulmigu Kalasalingam
College of Pharmacy, Anand Nagar,
Krishnankoil, Srivilliputtur, Virudhunagr Dist-
626126,TN.
3
Professor and Principal, Arulmigu
Kalasalingam College of Pharmacy, Anand
Nagar, Krishnankoil, Srivilliputtur, Virudhunagr
Dist-626126,TN.
ABSTRACT:
A circadian rhythm is any biological process that displays an endogenus,
entrainable oscillation of about 24 hours.These 24 hour rhythms are driven by a
circardian clock, and they have been widely observed in plants,animals,fungi and
cyanobacteria. The formal study of biological temporal rhythms, such as daily, tidal,
weekly, seasonal and annual rhythms is called chronobiology.In medical science, an
abnormal circardian rhythm in humans is known as circardian rhythm disorder.In
2017, the noble prize in medicine was awarded for the discoveries of molecular
mechanisms controlling the circardian rhythm.
KEY WORDS: Circardian rhythm, Biological clock, Chronobiology.
A REVIEW ON CIRCADIAN RHYTHM:
INTRODUCTION :
Circadian rhythms are driven by an internal biological clock that anticipates day/night
cycles to optimize the physiology and behavior of organisms. The formal study of
biological temporal rhythms, such as daily, tidal, weekly, seasonal and annual
rhythms is called chronobiology. In medical science, abnormal circadian rhythm in
humans is known as circadian rhythm disorder. In 2017, the noble prize in medicine
was awarded for the discoveries of molecular mechanisms controlling the circadian
2. rhythm.
Fig.1 represents some features of the human circadian(24-hour) biological clock
CONTROLLING CENTRE IN MAMMALS:
Suprachiasmatic nucleus (SCN) present in the hypothalamus of the brain controls the
circadian rhythm in mammals. There is a direct pathway between Lateral Geniculate
Nucleus (LGN) in the thalamus and SCN.
Thalamus ( LGN)
Retina
Hypothalamus
(SCN)
Although circadian rhythm is endogenous, they are adjusted to external environment
also.
EXTERNAL FACTORS:
1. Light
2. Temperature
3. Redox cycle
THE NATURAL HUMAN CIRCADIAN RHYTHM TO BE CLOSER TO 24
HOURS AND 11 MINUTES.
BIOLOGICAL MARKERS FOR THE ESTIMATION OF TIMING:
Melatonin
3. Minimum core body temperature
Plasma level of cortisol
MELATONIN SECRETION : Along day and night SCN receives information from
the retina of the eye, interprets it, and passes it on to the pineal gland in the
epithalamus. In response, the pineal gland secretes the hormone melatonin. Secretion
of melatonin peaks at night and lowers during the day
Fig.2 represents the temperature cycle
GENES:
1. Timeless gene- TIM
2. Period gene- PER
In fruit fly neurons these two proteins were identified. The synthesis of these proteins
is initiated by genes which direct mRNA to leave the cell nucleus. The reason that this
process is offered as an example of a mechanism sensitive to circardian rhythm is that
the protein synthesis varies with light and dark cycle.
Fig.3 represents the interaction of PER and TIM in the cytoplasm and
negative feedback loop in the nucleus
No light – PER and TIM combines and their own productions are suppressed
Presence of light- TIM protein destroyed immediately after synthesis. So it cannot
combine with PER. So PER controls photoentrainment ( light cycle)
4. DISRUPTIONS CAUSED IN CIRCADIAN RHYTHM AND HEALTH
PROBLEMS:
Fig.4 represents some mechanisms involved in the disruption of circadian
rhythm
Health problems can result from a disturbance to the circadian rhythm. Circadian
rhythm also plays a part in the reticular activating system, which is crucial for
maintaining a state of consciousness. A reversal in the sleep- wake cycle may be a
sign of uremia, acute renal failure. Disruption of the circadian clock work with the
external environment (e.g., light-dark cycle) might play a role in the development of
diabetes, obesity and psychological disorders like bipolar disorder
DRUGS AFFECTING CIRCADIAN RHYTHM AND CHRONOTHERAPEUTICS:
Abusing and habit forming drugs like cocaine, alcohol disrupts the circadian
pacemaker. These disrupted rhythms can increase for substance abuse.
Chronotherapy, also called as chronotherpeutics, refers to the use of circadian cycle of
a condition’s symptoms or the individual being treated in the application of therapy. It
is used in various clinical fields such as the treatment of asthma, cancer, hypertension,
depression and bipolar disorder. The methods of pharmaceutical chronotherapy
includes,
Imitative: copying the natural changes in a certain substance in the body.
Preventive: taking medicines at the moment that they are most necessary, for
example taking anti-hypertensives at the time of the day that the blood
pressure is rising.
Wake therapy: it is a form of sleep deprivation used as a treatment for
depression. The patient is made to awake all night. While feeling sleepy,
patient finds that their depression vanishes, until they sleep again.
CONCLUSION:
5. The discovery of self-sustained transcription or translation as the central
component of the molecular mechanism by which clock genes control
circadian oscillators in cells and tissues has led to new path in our
understanding of how organisms anticipate and adapt to the regular daily
environmental factors like light. This circadian rhythm has an important
implication in our health and well being. It seems that biorhythms are
necessary for all living systems and they are therefore, evolutionally
conservative. Mechanisms for their control are complex that knowledge
concerning them depends on the discovery of most characteristics of life; this
may be the reason why we are still far from knowing them fully.
ACKNOWLEDGEMENTS:
We whole-heartedly thank the management of our institution for giving us an
opportunity to present this poster.
AFFLIATION:
Presenting Author- M.Arumugavignesh, II Pharm D,Arulmigu Kalasalingam
College of Pharmacy, Anand Nagar, Krishnankoil, Srivilliputtur, Virudhunagr Dist-
626126,TN. Mobile :8072046740, Mail ID – m.arumugavignesh20@gmail.com
†Corresponding Author – Dr.V.Lavakumar,Professor and Research Coordinator,
Arulmigu Kalasalingam College of Pharmacy, Anand Nagar, Krishnankoil, Srivilliputtur,
Virudhunagr Dist-626126,TN.Mobile:+91 9494804367; Mail Id-
lavanyalavakumar@gmail.com.
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M.W. (1995).
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