Open AccessDistance‐based Permutation of Inter‐Meal Differences as a Sensitive Test of Temporomandibular Joint Nociception in Rats
Author(s) -
Umorin Mikhail,
Kramer Phillip R.,
Bellinger Larry L.
Publication year - 2017
Publication title -
journal of applied biobehavioral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.448
H-Index - 26
eISSN - 1751-9861
pISSN - 1071-2089
DOI - 10.1111/jabr.12067
Subject(s) - nociception , meal , analysis of variance , saline , medicine , repeated measures design , anesthesia , mathematics , statistics , receptor
We compare nonparametric permutation method using intra‐meal rate as endpoint with existing ANOVA method that uses average daily meal duration as an endpoint for detection of chronic pain in Sprague‐Dawley rats. Nociception following bilateral temporomandibular joint ( TMJ ) injection of high dose of Complete Freunds Adjuvant ( CFA , 250 μg/50 μL per side) could be detected in young adult male Sprague‐Dawley rats using average daily meal durations as a measure of nociception for up to 19 days (Kramer, Kerins, Schneiderman & Bellinger, Physiology & Behavior , 99, 2010; 669) using ANOVA and multiple comparison range tests. In this study, we reanalyzed the data using a nonparametric permutation procedure based on absolute differences between intra‐meal feeding rate curves. In addition to that experiment, we injected bilaterally the TMJ of naive rats with either a low‐dose CFA (15 μg/50 μL per side, n = 6) or saline (50 μL of 0.9%, n = 4) and monitored the animals for 7 days. The permutation test of the intra‐meal feeding rate detected the presence of nociception in the high‐dose CFA treatment group for up to 40 days or twice as long as when using ANOVA on average daily meal durations. The permutation method also detected the low‐dose CFA ‐induced nociception with ten times lower p‐ values and for several days longer than ANOVA of changes in meal durations. CFA ‐induced injury resulted in even reduction in intra‐meal feeding rate and lengthening of the meals in both high‐ and low‐dose CFA ‐injected animals. The rate analysis also showed when the rats first started a meal they were experiencing the same level of nociception as at the end of the meal. This demonstrated that intra‐meal chewing itself did not alter the level of nociception. These results suggest that permutation tests based on differences in intra‐meal feeding rates can be used as a sensitive test to determine and study the temporal patterns of TMJ nociception.