Method: Male Wistar rats received bilateral intra-articular administration of 50 uL of CFA or saline. To confirm the development of the inflammatory process was performed the quantification of the plasma extravasation in TMJs, by Evans Blue test. For the assessment of orofacial mechanical sensitivity, we used the Von Frey test. To access the anxiety level were evaluated the exploratory activity in the elevated plus maze (EPM). All tests were performed at 1, 3, 7 and 10 days after the induction of temporomandibular inflammation.
Result: The administration of CFA was able to promote greater plasma extravasation in the TMJ when compared to animals without inflammation (F5,78 = 6,06, p < 0.001). The CFA administration promoted orofacial mechanical allodynia. There was a significant difference between time and treatment for all groups. The EPM showed a statistical difference between treatments for the group of 1 day, in the number of entries in the open arms (F1,7 = 6.75, p = 0.041) and diving head (F1, 7 = 49, p < 0.001). In the group with 7 days of inflammation, a significant increase in immobility behavior (F1,7 = 40, p < 0.001) was observed. At 10 days, there was a significant increase of entries in the open arms in control animals (F1,9 = 6.66, p = 0.033).
Conclusion:
These results showed that injection of CFA in the TMJ of rats produces profound inflammatory response and occurs modifications in emotional behavior of rats with inflammation. It is also known that there is a relationship between the intensity of orofacial pain sensitivity and emotional state.