engleski

TRPV1 Channel-Mediated Bilateral Allodynia Induced By Masseter Muscle Inflammation

Objective: Objectives: To investigate whether unilateral inflammation of masseter muscle can cause bilateral allodynia, and whether the changes in nociception are regulated by TRPV1 channels. Method: Methods: Induction of masseter muscle inflammation in rats was carried out by unilateral injection of 50 μL of complete Freund's adjuvant. To evaluate nocifensive behavioral response head withdrawal threshold was measured at different time points using a von Frey anesthesiometer. After behavioral assessment, both right and left trigeminal ganglia were dissected and examined for histopathology and TRPV1 mRNA expression using quantitative real-time PCR analysis. Involvement of hippocampal TRPV1 in bilateral allodynia was examined after intrahippocampal injection of TRPV1 antagonist in CFA injected rats. Result: Results: Unilateral inflammation of masseter muscle induced bilateral allodynia. A significant increase in TRPV1 mRNA expression occurred in TRG ipsilateral to CFA injected masseter muscle, whereas no significant alteration in TRPV1 occurred in the contralateral TRG. Interestingly, central injection of TRPV1 antagonist 5-iodoresiniferatoxin into the hippocampus significantly attenuated the head withdrawal response of both CFA injected and non-CFA injected contralateral masseter muscle. Conclusion: Conclusions: Our findings indicate that upregulation of TRPV1 at the TRG level is due to nociception caused by inflammation, whereas contralateral nocifensive behavior in masticatory muscle nociception is likely mediated by central TRPV1, pointing to the involvement of altered information processing in higher centers.

Animal; Gene expression; Inflammation; Pain and TMJ and masticatory muscles

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