When we used rat thoracic aorta we faced some problems such as some rat aorta having a high response to Phenylephrine for contraction while others had slow responses to PE to induced contraction.
We also have similar results with wistar rats in our team, sometimes the results are contradictory, so we performed the test many times, with differents rats (generally 5 or 7) and we consider the tendance that is exhibited by the majority
These variations may occur depending on the presence or absence of endothelium. Endothelium blunts the vasoconstrictor responses to phenylephrine in the aorta of Wistar rats. Mechanical removal of the vascular endothelium is not very easy. To test the presence of the vascular endothelium is necessary to assess the vasodilator response to acetylcholine.
I would say that such variation is normal between animals. We often see different sensitivies to compounds between animals, batches of rats, strains of rats etc etc. Sometimes even different segments of the same artery will behave differently in different organ baths. I imagine the variation is due to a plethora of reasons like quality of the dissection, handling of the arery during mounting, organ bath temperature, oxygen tensions, health of the animal, age of the animal, hweterogeneity in the expression of the various receptors invovled from one animal to another, and from one segment of artery to another...and probably lots more reasons!
Thank you Mireille Kameni
Thank you Cristina Antoniali
Thank you Saoirse Elizabeth O'Sullivan
Thanks for all you gave me more information about my problem
You need control a number of parameters (as indicated Dr. O'Sullivan) including basal tension and cross-sectional area but endothelium functional integrity appears to be more important (as Dr. Antoniali supposed).
I realy care about the endothelium. I never touch the aorta or strech it during the dissection. I touch only the surroinding of fat tissue, lay it on paraffin block with several drop of Krebs on it, divide it new sharp blade.
I think randomization is important:
When I divide the thorasic aorta in to four, the top segment always give more tension. I places each segment in to different bath every time, not in order. (my system has 4 transducers and bath). So every day, for example, the first transducer records different segment.
Additionally, I change the drug incubations too. For example the first channel is with Silymarin (SM), the second INDO+SM, the third LNAME+SM, the forth is control,. The next time I label the baths randomly in different way.
Do not forget to brush the glass chambers properly end of experiment with a lots of distilled water for next day. we have to get rid of remains!
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