Expert: Florence M Rollwagen - 4/7/2009

Question
QUESTION: Hello, I am trying to see if there is a way of raising the blood pressure of planaria? I have been reading that caffeine will cause planaria's heart beat faster. Will it be valid to say if the heart rate is increased the blood pressure will be increased also? Thank you for all you help.

ANSWER: Hi Natasha:  Alas, you cannot do this experiment.  Planaria don't have circulatory systems or hearts.  I don't know what you've read where caffeine raises the heart rate of planaria.  They don't have hearts.

Here's a link:

http://intro.bio.umb.edu/111-112/112s99Lect/bodyplans/planarian.html

Hope this helps.  Write back if you have more questions.

FM Rollwagen, PhD

---------- FOLLOW-UP ----------

QUESTION: Thank you for such a quick reply. Sorry for the mistake. I have been trying to figure out what would be best for doing as an experiment at home.  I must have thought about Daphnia. Do you think experimenting with daphnia then will be valid to say that if the heart rate is raised, the blood pressure is raised as well? I have read a lot about the grape seed extract and was wondering if it can help to lower the blood pressure. That is why I am trying to raise the blood pressure of invertebrates. If you have any other living organism that you think I can use, I would love to hear your opinion and suggestions.  Thank you very much in advance.

Answer
Hi again, Natasha:  I admire your attempt to do experiments at home.  But before you start, make sure you have some equipment present.

First, how will you measure heart rate?  Daphnia are small, and you will need a microscope.  You will need a stopwatch or timer to count the beats per minute under the microscope.

Second, you need a source of Daphnia.  If you want to gather them from ponds, can you identify them?

Third, heart rate is not always related to blood pressure, so you cannot make the assumption that if heart rate goes up, that bp will also.

Fourth, and perhaps most importantly, how will you administer the drug.  If you want to put it into the water, you will have to be sure that it gets inside the Daphnia body.  And dosage will be critical.  You will have to measure the volume of water, the number of organisms/volume and then add the drug in measured doses.  And for varying amounts of time.  

Logistically this could be a problem too.  If you start with 10 Daphnia per group (let's say).  After you add the drug and start measuring heart rate, it may take up to 20 minutes to measure them all.  So the last Daphnia measured will have been exposed to the drug longer than the first one.

I'm not trying to discourage you, not by any means.  I'm trying to let you know that science is all about measurement and controlling the conditions.  Unless you can do this effectively and quickly, you may not get useful information.

And don't forget, it will take many, MANY trials for you to get this right, so plan on a long Saturday afternoon [grin].

Write back when you've figured this all out, and we'll talk some more.

FM Rollwagen, PhD