Voluntary biting behavior as a functional measure of orofacial pain in mice

Abstract

Introduction: Pain-related behavior secondary to masticatory function can be assessed with the rodent bite force model. A reduction of the bite force has been shown to be related to pain associated with the masseter muscle and jaw activity, while an increase in bite force suggests improvement of muscle function and less pain. To evaluate the usefulness of the bite force measure in studying long-lasting orofacial pain we analyzed biting parameters during prolonged myofascial pain induced by ligation injury of the masseter muscle tendon (TL) in mice. Methods: C57BI/6 mice were habituated to bite at a pair of aluminum plates attached to a force displacement transducer. The transduced voltage signals were amplified and converted to force through calibration with a standard weight set. Voluntary biting behavior was recorded for 100 seconds/session and those with bite forces ≥ 980 mN were analyzed. Nociception was also verified with von Frey, conditioned place avoidance (CPA) tests and mouse grimace scale. Persistent orofacial pain was induced with unilateral ligation of one tendon of the masseter muscle (TL). Results: To reduce interference of random bites of smaller forces, the top 5 or 15 bite forces (BF5/15) were chosen as a measure of masticatory function and related to pain behavior. Both male and female mice exhibited similar BF5/15. For the first nascent test of all mice, mean bite force was significantly and positively correlated with the body weight. However, this correlation was less clear in the latter tests (2-8 w). TL induced a reduction of BF5/15 that peaked at 1 w and returned to the baseline within 3 w. The von Frey and CPA tests indicated that mechanical

TRPV1 and TRPV1-Expressing Nociceptors Mediate Orofacial Pain Behaviors in a Mouse Model of Orthodontic Tooth Movement

“…In experiments involving behavioral assays, 12-week-old mice were used for stable measurement of bite force (BF) behaviors (Wang et al, 2017a). Orthodontic pain shows limited or no clear sex difference (Jones, 1984; Ngan et al, 1989; Scheurer et al, 1996), whereas mouse behavioral assays, especially BF measurement, are influenced by sex; when both male and female mice are included in pain assays, variation of the data increases (Guo et al, 2019b). To facilitate establishing a model of orthodontic pain in mice, we have focused on male mice without attempting to determine sex differences at this time.…”

“…Mouse grimace scale (MGS) and BF were performed as previously described (Wang et al, 2017a, 2018; Guo et al, 2019b). All behavioral assays and video analysis were performed in a blinded manner.…”

Phosphorylation of TRPV1 S801 Contributes to Modality-Specific Hyperalgesia in Mice

“…Bite force assay. To assess bite-evoked pain associated with craniofacial muscle inflammation in mice, we performed a bite force assay as previously described (Wang et al, 2017(Wang et al, , 2018Guo et al, 2019). Mice were acclimated to the testing environment and handling for 2 d before behavioral testing.…”

Methods Used and Application of the Mouse Grimace Scale in Biomedical Research 10 Years on: A Scoping Review

“…In the majority of cases (31 studies), data from these tests corroborated MGS scoring. In the remaining studies, either no association was seen with the chosen measures [ 26 , 53 , 58 , 72 ], or there was unclear reporting or a lack of direct comparison in the same animals [ 39 , 45 ].…”