[Abstract Title]. - Society for Neuroscience

database of comparative potency across a spectrum of mechanisms of action could be created,
providing a basis for cross species scaling to man and hence efficacious dose prediction.
Disclosures: L. Corradini, None; T. Pitcher, None; N. Benson, None; J.G. Wheeler, None; B.
Tran, None; F. Khedache, None; I. Machin, None; K. Tan, None; M.J. Field, None; H.
Mansikka, None.
Poster
267. Pain: Pain Models II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 267.10/FF16
Topic: D.08.j. Pain models
Support: CIHR
FRSQ.
Title: Evaluation of chronic pain induced by injections of acidic saline into the masseter muscles
of rats
Authors: N. L. CARAM-SALAS 1,3 , *A. KOLTA 1,4 , J. P. LUND 2,4 ;
1 Dept Physiol, 2 Physiologie, Univ. Montreal, Montreal, QC, Canada; 3 Dent. Fac., 4 Dent. faculty,
Mc Gill Univ., Montreal, QC, Canada
Abstract: Animal models are needed to help uncover the aetiology of chronic orofacial muscle
pain conditions. Lactic acid produced by heavy exercise is a natural stimulus for muscle
nociceptors, and Sluka et al (Muscle Nerve. 2001, 24(1):37-46) have shown that repeated
injections of acidic saline (AS; pH 4) into leg muscles of rodents induce long-lasting signs of
allodynia/hyperalgesia. Similar injections into jaw muscles have been yielding contradictory
results. In rats, Ambalavanar et al. (Neuroscience. 2007, 149(3):650-9) reported no changes in
nociceptive behaviour or in CGRP expression in muscle afferent neurons in the trigeminal
ganglion, while Morris and Widmer (Soc. Neurosci. Abstr., 2007) did see changes in mastication
and in the expression of several peptides in mice. We have previously shown changes in the
excitability of jaw-closing muscle spindle afferents or rats following 2 injections of AS that
appeared within 24hrs after the first injection and that lasted between 35 and 42 days. The aims
of this study were: (1) To show that repeated AS injections into the masseter muscle induce longlasting
nocifensive behaviour in rats, (2) To determine whether a single injection could be used
and (3) To evaluate whether the effects are bilateral or unilateral. Nocifencive behaviour was
evaluated at different time points before and after injections by determining the frequency of