Light, circadian cycles, and cardiac function

Doug Jones dlj at raptor.physiol.unimelb.edu.au
Fri Apr 22 01:14:56 EST 1994

David Hallowell (st93q84w at Dunx1.OCS.Drexel.Edu) wrote:
: I'm not sure if this really is the correct place to post this but...I'm
: interested in testing the relationship between circadian rhythms and
: cardiac function and the affect that light might have on this relationship
: for a class project.
: How would I go about doing this?  I have a clue how to test this 
: generally, but I'm not sure on the specifics: what organism to use, how 
: to test for changes in cardiac function....

: It's too hard to use humans since I can't think of anyone that is willing
: or has the time to undergo light depravation for this experiment.  Can
: heart rate and/or blood pressure be measured in mice?  Does anyone know of
: any organisms that might prove to be easiest to study?

: Any help or insight is great appreciated!

: David

You can get some information on alterations in cardiac performance by
using a Holter Monitor. This records heart beats in time and with a
decoder can generate alterations in heart intervals over a 24 hour
period. Also you can use programs which determine the standard
deviation in the "R-R intervals". This information provides some
indication of the autonomic influence over the heart during the
24 hour period - AND has been used as one index of the potential
health/dysfunction of the autonomic controls.

Your local heart association should also be able to provide you with
some of the results of studies which indicate the potential of these
measurements to determine subjects as risk of sudden death.

If you are interested in testing the effects of light, AND IF your
institution has environmental chambers, you could try having a couple
of friends spend a weekend (friday night to sunday night) in the
chamber with a reverse light cycle and see if there are any shifts in
their heart rate variability.

Others might be able to suggest experiments with mice or rats.
Certainly there is the ablility to measure heart rate, and even blood
pressure from many rodent species.

Good luck!

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