Injection of adjuvant but not acidic saline into craniofacial muscle evokes nociceptive behaviors and neuropeptide expression
| Autor: | Dean Dessem, Ranjinidevi Ambalavanar, Chandra Yallampalli, Uma Yallampalli |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Male
medicine.medical_specialty Hot Temperature Calcitonin Gene-Related Peptide medicine.medical_treatment Radioimmunoassay Facial Muscles Neuropeptide Hindlimb Sodium Chloride Calcitonin gene-related peptide Injections Intramuscular Article Rats Sprague-Dawley Masseter muscle Trigeminal ganglion Facial Pain Physical Stimulation Internal medicine medicine Animals Neurons Afferent Saline Acid-sensing ion channel Adjuvants Pharmaceutic Pain Measurement Behavior Animal Masseter Muscle business.industry General Neuroscience Neuropeptides Hydrogen-Ion Concentration Immunohistochemistry Rats Nociception Endocrinology Trigeminal Ganglion Anesthesia business |
| Zdroj: | Neuroscience. 149:650-659 |
| ISSN: | 0306-4522 |
| DOI: | 10.1016/j.neuroscience.2007.07.058 |
| Popis: | Craniofacial muscle pain including muscular temporomandibular disorders accounts for a substantial portion of all pain perceived in the head and neck region. In spite of its high clinical prevalence, the mechanisms of chronic craniofacial muscle pain are not well understood. Injection of acidic saline into rodent hindlimb muscles produces pathologies which resemble muscular pathologies in chronic pain patients. Here we investigated whether analogous transformations occur following repeated injections of acidic saline into the rat masseter muscle. Injection of acidic saline (pH 4) into the masseter muscle transiently lowered i.m. pH to levels comparable to those reported for rodent hindlimb muscles. Nevertheless, repeated unilateral or bilateral injections of acidic saline (pH 4) into the masseter muscle failed to alter nociceptive behavioral responses as occurs in the hindlimb. Changing the pH of injected saline to pH 3.0 or 5.0 also did not evoke nocifensive behavior. Acid sensing ion channel 3 receptors, which are implicated in transformations following acidification of hindlimb muscles, were found on trigeminal ganglion muscle afferent neurons via combined neuronal tracing and immunocytochemistry. In contrast to the acidic saline, injection of complete Freund's adjuvant (CFA) into the masseter muscle induced mechanical allodynia for 3 weeks, thermal hyperalgesia for 1 week and an increase in the number of calcitonin gene-related peptide (CGRP)-immunoreactive muscle afferent neurons in the trigeminal ganglion. Although pH may alter CGRP release in primary afferent neurons, the number of CGRP-muscle afferent neurons did not change following i.m. injection of acidic saline. Further, there was no change in ganglionic iCGRP levels at 1, 4 or 12 days after i.m. injection of acidic saline. While these findings extend our earlier reports that CFA-induced muscle inflammation results in behavioral and neuropeptide changes they further suggest that i.m. acidification in craniofacial muscle evokes different responses than in hindlimb muscle and imply that disparate proton sensing mechanisms underlie these discrepancies. |
| Databáze: | OpenAIRE |
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