PMID- 17379421
OWN - NLM
STAT- MEDLINE
DCOM- 20070703
LR  - 20220309
IS  - 0306-4522 (Print)
IS  - 0306-4522 (Linking)
VI  - 146
IP  - 3
DP  - 2007 May 25
TI  - Role of peripheral mu-opioid receptors in inflammatory orofacial muscle pain.
PG  - 1346-54
AB  - The aims of this project were to investigate whether inflammation in the 
      orofacial muscle alters mu opioid receptor (MOR) mRNA and protein expressions in 
      trigeminal ganglia (TG), and to assess the contribution of peripheral MORs under 
      acute and inflammatory muscle pain conditions. mRNA and protein levels for MOR 
      were quantified by reverse-transcription-polymerase chain reaction (RT-PCR) and 
      Western blot, respectively, from the TG of naive rats, and compared with those 
      from the rats treated with complete Freund's adjuvant (CFA) in the masseter. TG 
      was found to express mRNA and protein for MOR, and CFA significantly up-regulated 
      both MOR mRNA and protein by 3 days following the inflammation. The MOR protein 
      up-regulation persisted to day 7 and returned to the baseline level by day 14. We 
      then investigated whether peripheral application of a MOR agonist, D-Ala2, 
      N-Me-Phe4, Gly5-ol-enkephalin acetate salt (DAMGO), attenuates masseter 
      nociception induced by masseteric infusion of hypertonic saline (HS) in lightly 
      anesthetized rats. DAMGO (1, 5, 10 microg) or vehicle was administered directly 
      into the masseter 5-10 min prior to the HS infusion. The DAMGO effects were 
      assessed on mean peak counts (MPC) and overall magnitude as calculated by the 
      area under the curve (AUC) of the HS-evoked behavioral responses. Under this 
      condition, only the highest dose of DAMGO (10 microg) significantly reduced MPC, 
      which was prevented when H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP), a 
      selective MOR antagonist, was co-administered. DAMGO pre-treatment in the 
      contralateral masseter did not attenuate MPC. The same doses of DAMGO 
      administered into CFA-inflamed rats, however, produced a greater attenuation of 
      both MPC and AUC of HS-evoked nocifensive responses. These results demonstrated 
      that activation of peripheral MOR provides greater anti-nociception in inflamed 
      muscle, and that the enhanced MOR effect can be partly explained by significant 
      up-regulation of MOR expression in TG.
FAU - Nunez, S
AU  - Nunez S
AD  - Department of Biomedical Sciences, Program in Neuroscience, University of 
      Maryland Baltimore School of Dentistry, 650 West Baltimore Street, Baltimore, MD 
      21201, USA.
FAU - Lee, J-S
AU  - Lee JS
FAU - Zhang, Y
AU  - Zhang Y
FAU - Bai, G
AU  - Bai G
FAU - Ro, J Y
AU  - Ro JY
LA  - eng
PT  - Journal Article
DEP - 20070326
PL  - United States
TA  - Neuroscience
JT  - Neuroscience
JID - 7605074
RN  - 0 (Analgesics, Opioid)
RN  - 0 (Receptors, Opioid, mu)
RN  - 100929-53-1 (Enkephalin, Ala(2)-MePhe(4)-Gly(5)-)
RN  - 9007-81-2 (Freund's Adjuvant)
SB  - IM
MH  - Analgesics, Opioid/pharmacology
MH  - Animals
MH  - Behavior, Animal/physiology
MH  - Blotting, Western
MH  - Dose-Response Relationship, Drug
MH  - Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
MH  - Facial Pain/*physiopathology/psychology
MH  - Freund's Adjuvant
MH  - Functional Laterality/physiology
MH  - Inflammation/chemically induced/*physiopathology/psychology
MH  - Male
MH  - Masseter Muscle/metabolism
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Receptors, Opioid, mu/biosynthesis/genetics/*physiology
MH  - Reverse Transcriptase Polymerase Chain Reaction
MH  - Trigeminal Ganglion/metabolism
EDAT- 2007/03/24 09:00
MHDA- 2007/07/04 09:00
CRDT- 2007/03/24 09:00
PHST- 2006/12/04 00:00 [received]
PHST- 2007/02/07 00:00 [revised]
PHST- 2007/02/09 00:00 [accepted]
PHST- 2007/03/24 09:00 [pubmed]
PHST- 2007/07/04 09:00 [medline]
PHST- 2007/03/24 09:00 [entrez]
AID - S0306-4522(07)00173-X [pii]
AID - 10.1016/j.neuroscience.2007.02.024 [doi]
PST - ppublish
SO  - Neuroscience. 2007 May 25;146(3):1346-54. doi: 
      10.1016/j.neuroscience.2007.02.024. Epub 2007 Mar 26.