I´ve measured mechanic allodynia with von Frey filaments with different methods, such as Chaplan`s and measuring percentage of responses, but I think its failed. I couldn`t see if our molecule works in a carrageenan inflammation model.
For human studies, The German research network published articles on the standardised protocol for QST . From instance: Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values. There are videos and detailed descriptions of each technique if you have access to the articles. It's of course for humans and animal protocols are different. Which are you interested in?
I have used two methods to asses mechanical allodynia in rats using Von Frey hair test. First one is digital Von Frey meter by IITC in which you use only one hair and the force at which animal withdraws paw is recorded in digital meter. Another and the most widely used method is up down method in which you apply hairs of different forces in the sub plantar region of rat hindpaw and then depending upon the paw withdrawal response by rat next time you use hair of another force. For example if at one force rat withdraw paw then next time you should use the hair of lower force and vice versa. I would recommend you to go for up down method. Pleaselet me know if you need reference article for this method.
In my lab we're currently using mechanical thresholds to examine migraine tendencies in a mouse model. We have found that the Chaplan method is not reliable enough as it is difficult to weed out false positives/negatives with one response. Instead, we have been using a 5-try paradigm. Essentially, we do the Von Frey test 5 times in a row on one hindpaw while the animal is not moving. If the animal moves, we repeat the process until we get a reading where the animal is not moving around. As soon as the non-moving animal responds to the fiber (as long as it's within the 5 non-moving trials), we count it and move on to the next animal. If they don't respond in the 5 trials, we consider it a no response and move on. For each hindpaw we obtain a threshold going from low weight fiber to high weight fiber and then from high weight fiber to low weight fiber and get an average threshold.
Sine you are using a carrageenan model and referenced the Chaplan paper, I am going to assume that you are measuring this in rodents. We use the Dixon up and down method (Dixon, 1965 JASA). The basic premise is that for mice you start with the VF filament #5 (in a standard kit) and then based on the animals response you either move to the next highest filament or the next lowest (up and down). For example, the animal does not respond to filaments 5,6 or 7 but withdraws on 8, then you move down to 7. Following the first change in direction (up to down or down to up) you then determine the responses to the next 4 applications (regardless of whether the mouse responds or not). This is the same for the rat except the starting filament is 9.
Alternatively, a lot of labs have used a variation of the Chaplan method and gotten good results.
If you want more info on the up and down method (like the macro we use to calculate the up and down pattern into grams) then feel free to contact me.
I personally prefer the electronic von Frey for the evaluation of allodynia. You will just have to apply the electronic von Frey 4 times and do the average of the paw withdrawal pressure or weight. Two consecutive applications must be separated by at least 5 minutes. For allodynia, this method is more reliable than the up and down. But if you do not have electronic von Frey, then you use the up and down method. The frequency (evaluating the percentage of paw withdrawal over the total number of application of precise von Frey hair) is suitable for the evaluation of hyperalgesia but not for allodynia.
Thanks Télesphore!! I appreciated your comment. We work with rats and what we have in our lab is von Frey filamments not the electronic one, so we have tried with both methods: the up-down and the percentage of paw withdraw. In the first case we noted that the individual variation was very high and the statistical analysis was terrible, then we tried with the percentage method. At that time, we observed that we had negative-false in our experiment, because the indomethacin, which has been long reported as anti-infalmmatory drug, didn´t work in carrageenan model. I think if I try with Chaplan variation method, I probably will obtein better results in our experiments. Don´t you?Thank everyone for helping me.
Yes, of course. The test to map the static mechanical allodynia with von Frey filament is the allodynography (Spicher et al., Somatosens Mot Res 2008)
http://doc.rero.ch/lm.php?url=1000,43,2,20080507152616-JF/rouiller_sma.pdf
They are a lot of paper ont this topic on www.neuropain.ch
http://www.neuropain.ch/sites/default/files/documents/list_of_publications_dpt_research_somatosensory_rehab_network.pdf
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