If you are concerned with volume of blood available, rats are better.  Ask Rob Wheaton at [email protected] about our "mouse notebook"

Dear Sherouk,

Evaluation of anticoagulant or hemorrhagic potential of drugs could be reasonably done in rats because there are some very well established models in rats.  I can site at least three models.  One is the Rat tail transection bleeding model in rats established by Dejana.  This entails administration of the drug either intravenously , subcutaneously or orally and after an appropriate time, the rat tail is transected with the simultaneous start of the stop watch and the blood on the transected tail blotted by a filter paper every 30 seconds until the blood stops to ooze and a primary hemostatic plug is formed to stop the bleeding at which time the stop watch is stopped and the time recorded.  This is the bleeding time.  You can evaluate the bleeding potential of a drug by comparing the anticoagulant drug compared to a saline control in this model.  The second model in rats is the Jugular vein clamping model developed by Wolfram Raake.  This is again a well-established model to evaluate the anticoagulant potential of an anticoagulant by counting the number of clamps required to form a defined clamp in the  jugular vein.  The number of clamps required to form a clot is a reflection of the anticoagulant potential of the drug.  The third model is the Rat mesenteric venule Laser model developed by Breddin and Weichert.  This is by far the most physiologic model to test the anticoagulant potential of anticoagulant drugs.  This entails the delivery of the rats mesentery following anesthesia and checking the blood flow in the venule of the mesentery placed in a sline bath using an inverse microscope.  Following an administration of an anticoagulant or saline as a control a series of lase shots are placed on the venule using an argon laser with a specific energy.  The blood flow can be checked after each laser shot by looking through the inverse microscope,  You can actually visualize how the circulating platelets gets attracted to the site of the lase shot and how they get activated and aggregate forming a defined clot.  Again in this model the number of laser shots needed to form defined clot is a measure of the anticoagulant potential of the drug when compared to the saline control.  One can also slightly modify this model to evaluate the thrombolysis.

There are also animal models in arbbits but rats ofcourse are quite smaller.  So dear Sherouk, these are perhaps the reasons why people would like to select rats.  More importantly if you would like to draw blood samples one can place a catheter in the rat carotid and draw appropriate volumes of blood samples at defined intervals during the course of the experiment and these citrated blood samples could be centrifuged at 3000 rpm for 20 minutes to obtain the plasma which agin could be used to analyze for different coagulation parameters such as PT, APTT, TT and other tests.

Sherouk, I hope this answers your question.

Best Wishes and good luck,

Omer 

We tested different antithrombotic agents in rats. See for example:

https://www.ncbi.nlm.nih.gov/pubmed/26529577

https://www.ncbi.nlm.nih.gov/pubmed/16493492

Sincerely,

Mojca

Thank you all for your answers they were of great help.