Ligature of Masseter Tendon Invokes Nociception Determined by Meal Duration

Objectives: Temporomandibular joint (TMJ) inflammation induces a pain response in rats that can be measured by quantitating changes in feeding behavior but the inflammatory model does not always reflect muscle pain seen in patients. Recent studies have found that ligature of the masseter muscle will induce a persistent muscle pain response in rats as assayed with Von Frey filaments.  We were interested in determining whether another measure of nociception (feeding behavior) could detect the response after ligature of the masseter tendon.  In this report we used meal duration and meal number as a quantitative measure of the nociceptive response to bilateral ligation of the masseter tendon.

Methods: Two ligatures were placed around the tendon attachment of the anterior superficial portion of the masseter muscle.  The tendon on both sides of the head were ligated. Animals were placed in feeding units and meal patterns were measured from one day before the ligatures were placed to 18 days following ligature surgery.  The rats were on a 10:14 dark:light cycle and were fed ad libitum. 

Results: Dark phase and daily meal duration were significantly affected (p<0.001) by ligature of the tendon for 18 days following surgery.   The ligature effect was significant during the dark phase meal duration from days 8 through 14 (p<0.05).  Daily meal number was significantly effected by ligature of the tendon for the first seven days (p<0.05).  Post-hoc testing indicated that consistent significant differences in meal duration and meal number could be detected versus the sham group. 

Conclusions: These findings suggest meal patterns are a quantitative measure of the nociception produced after ligature of the masseter tendon in male and female rats.