Background & Aims

The commonly used Von Frey filaments are productive in evaluating behavioural responses of pain in preclinical and clinical research. To reduce the potential experimenter bias, automated instruments were developed for behavioural assessment. In preclinical research, pain models of teeth extraction are employed to screen the analgesic drugs to treat symptoms like allodynia and hyperalgesia. The present study aimed to compare the nociceptive response in response to the use of conventionally used Von Frey monofilaments and an automated esthesiometer using the model of nociception induced by tooth extraction in rats.

Methods

Adult male Wistar rats (200-250 g) were used (n=6/group). Animals were divided into 4 groups: 1 – Naïve Von Frey filaments (VFF), 2 – Surgical VFF, 3 – Naïve Digital Von Frey (DVF) and 4 – Surgical DVF. The animals were anesthetized, the lip and tongue were gently pulled away, the gum away from the molars with decollators. The teeth were loosened and removed by a gentle levering motion. the bleeding was stopped with a saline compress. Rats were handled and habituated to the testing environment at the same time of day for 3 days prior to the experiment. Mechanical sensitivity in the vibrissae was assessed by applying VFF and DVF on the 1st, 2nd, and 3rd postoperative days. The head withdrawal threshold upon mechanical stimulation of the vibrissae was defined as the minimum pressure required to evoke a leak more than 3 times out of 5 stimuli.

Results

Animal’s responsiveness and sensitivity to tactile stimulation was assessed one day after teeth extraction. When tested with digital Von Frey, mean head withdrawal threshold of the pre-operated rats was 120.5 ± 47.6 g (media do baseline). On 1st postoperative day, head withdrawal threshold was 63.43 ± 10.56 g in operated animals (p=0,0008 vs Naïve DVF). When tested with monofilaments, consistent mechanical allodynia readings were observed in operated rats (35.5 ± 19.45 g; p<0.=0,0007 vs Naïve VFF).

Conclusions

The main advantage of digital Von Frey compared to manual Von Frey is that an increasing force is applied by a single filament. This therefore provides measure of paw withdrawal threshold on a continual scale, as the force is applied continuously and not in steps. However, here it was found that the response obtained with the Von Frey filaments was more sensitive than that obtained with the digital device. This difference in results may be related to the evaluator’s lack of experience with the model, but also to the fact that Von Frey filaments and digital Von Frey can activate different subsets of sensory neurons.

References

Deuis JR, Dvorakova LS, Vetter I. Methods Used to Evaluate Pain Behaviors in Rodents. Front Mol Neurosci. 2017 Sep 6;10:284. doi: 10.3389/fnmol.2017.00284.

Nirogi R, Goura V, Shanmuganathan D, Jayarajan P, Abraham R. Comparison of manual and automated filaments for evaluation of neuropathic pain behavior in rats. J Pharmacol Toxicol Methods. 2012 Jul;66(1):8-13. doi: 10.1016/j.vascn.2012.04.006.

Shepherd SD, O’Buckley SC, Harrington JM, Haines LG, Rothrock GD, Johnson LM, Nackley AG. A moldable sustained release bupivacaine formulation for tailored treatment of postoperative dental pain. Sci Rep. 2018 Aug 15;8(1):12172. doi: 10.1038/s41598-018-29696-w.

Presenting Author

Adriana Campos

Poster Authors

Adriana Barros

DSc

University of Fortaleza

Lead Author

E-mail

Pedro Jessé Veras MSc

Universidade de Fortaleza

Lead Author

E-mail

Gerlânia Leite PhD

Universidade Federal do Cariri

Lead Author

E-mail

Manoelly Deusimara Walraven BSc

Universidade de Fortaleza

Lead Author

E-mail

Sergio Marques Filho BSc

Uniateneu

Lead Author

E-mail

Topics

  • Models: Oral/craniofacial