title: Deep tissue inflammation upregulates neuropeptides and evokes nociceptive behaviors which are modulated by a neuropeptide antagonist.
abstract: Promising recent developments in the therapeutic value of neuropeptide antagonists have generated renewed importance in understanding the functional role of neuropeptides in nociception and inflammation. To explore this relationship we examined behavioral changes and primary afferent neuronal plasticity following deep tissue inflammation. One hour following craniofacial muscle inflammation ipsilateral as well as contralateral head withdrawal thresholds and ipsi- and contralateral hindpaw withdrawal thresholds were lowered and remained reduced for 28 days. Elevated levels of calcitonin gene-related peptide (CGRP) within the trigeminal ganglion temporally correlated with this mechanical allodynia. Inflammation also induced an increase in the number of CGRP and substance P (SP)-immunopositive trigeminal ganglion neurons innervating inflamed muscle but did not evoke a shift in the size distribution of peptidergic muscle afferent neurons. Trigeminal proprioceptive muscle afferent neurons situated within the brainstem in the mesencephalic trigeminal nucleus did not express CGRP or SP prior to or following inflammation. Intravenous administration of CGRP receptor antagonist (8-37) two minutes prior to adjuvant injection blocked plasma extravasation and abolished both head and hindlimb mechanical allodynia. Local injection of CGRP antagonist directly into the masseter muscle prior to CFA produced similar, but less pronounced, effects. These findings indicate that unilateral craniofacial muscle inflammation produces mechanical allodynia at distant sites and upregulates CGRP and SP in primary afferent neurons innervating deep tissues. These data further implicate CGRP and SP in deep tissue nociceptive mechanisms and suggest that peptide antagonists may have therapeutic potential for musculoskeletal pain.
authors.affiliation: Department of Biomedical Sciences, University of Maryland, Baltimore, 666 West Baltimore Street, MD 21201, USA Department of Oral Anatomy and Neurobiology, Osaka University, Osaka 565-0871, Japan Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Texas, Galveston, TX 77555, USA Department of Obstetrics and Gynecology, University of Texas, Galveston, TX 77555, USA.
authors.forename: Ranjinidevi
authors.initials: R
authors.lastname: Ambalavanar
authors.forename: Masayuki
authors.initials: M
authors.lastname: Moritani
authors.forename: Aicha
authors.initials: A
authors.lastname: Moutanni
authors.forename: Panduranga
authors.initials: P
authors.lastname: Gangula
authors.forename: Chandrasekha
authors.initials: C
authors.lastname: Yallampalli
authors.forename: Dean
authors.initials: D
authors.lastname: Dessem
mesh_terms: D000344:Afferent Pathways / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000378:metabolism; D006930:Hyperalgesia / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D009220:Myositis / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010446:Peptide Fragments / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000037:antagonists & inhibitors / Q000378:metabolism; D016896:Treatment Outcome; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D009479:Neuropeptides; D010446:Peptide Fragments; C058636:calcitonin gene-related peptide (8-37); D013373:Substance P; D015740:Calcitonin Gene-Related Peptide