Peripheral mGluR5 antagonist attenuated craniofacial muscle pain and inflammation but not mGluR1 antagonist in lightly anesthetized rats

• Published in: Brain research bulletin 2006-10, Vol.70 (4), p.378-385
• Main Authors: Lee, Ho Jeong, Choi, Hyo Soon, Ju, Jin Sook, Bae, Yong Chul, Kim, Sung Kyo, Yoon, Young Wook, Ahn, Dong Kuk
• Format: Article
• Language: English
• Subjects: Anesthetics, Local - therapeutic use; Animals; Antinociception; Behavior, Animal; Benzoates - therapeutic use; Dose-Response Relationship, Drug; Drug Interactions; Excitatory Amino Acid Antagonists - therapeutic use; Facial Muscles - drug effects; Facial Muscles - physiopathology; Facial Pain - chemically induced; Facial Pain - drug therapy; Functional Laterality - drug effects; Glycine - analogs & derivatives; Glycine - therapeutic use; Inflammation - chemically induced; Inflammation - drug therapy; Lidocaine - therapeutic use; Male; Muscle inflammation; Muscle pain; Mustard Plant; Nociceptive behaviour; Pain Measurement - methods; Peripheral mGluR; Plant Oils; Pyridines - therapeutic use; Rats; Rats, Sprague-Dawley
• ISSN: 0361-9230; 1873-2747
• DOI: 10.1016/j.brainresbull.2005.09.021

The present study investigated the role of peripheral group I metabotropic glutamate receptors (mGluRs) in MO-induced nociceptive behaviour and inflammation in the masseter muscles of lightly anesthetized rats. Experiments were carried out on male Sprague-Dawley rats weighing 300–400 g. After initial anesthesia with sodium pentobarbital (40 mg/kg, i.p.), one femoral vein was cannulated and connected to an infusion pump for intravenous infusion of sodium pentobarbital. The rate of infusion was adjusted to provide a constant level of anesthesia. Mustard oil (MO, 30 μl) was injected into the mid-region of the left masseter muscle via a 30-gauge needle over 10 s. After 30 μl injection of 5, 10, 15, or 20% MO into the masseter muscle, the total number of hindpaw shaking behaviour and extravasated Evans’ blue dye concentration in the masseter muscle were significantly higher in the MO-treated group in a dose-dependent manner compared with the vehicle (mineral oil)-treated group. Intramuscular pretreatment with 3 or 5% lidocaine reduced MO-induced hindpaw shaking behaviour and increases in extravasated Evans’ blue dye concentration. Intramuscular pretreatment with 5 mM MCPG, non-selective group I/II mGluR antagonist, or MPEP, a selective group I mGluR5 antagonist, produced a significant attenuation of MO-induced hindpaw shaking behaviour and increases in extravasated Evans’ blue dye concentration in the masseter muscle while LY367385, a selective group I mGluR1 antagonist, did not affect MO-induced nociceptive behaviour and inflammation in the masseter muscle. These results indicate that peripheral mGluR5 plays important role in mediating MO-induced nociceptive behaviour and inflammation in the craniofacial muscle.