title: Activation of dura-sensitive trigeminal neurons and increased c-Fos protein induced by morphine withdrawal in the rostral ventromedial medulla.
abstract: Aims Overuse of medications used to treat migraine headache can increase the frequency of headaches. Sudden abstinence from migraine medication can also lead to a period of withdrawal-induced headaches. The aim of this study was to examine the effect of morphine withdrawal localized to the rostral ventromedial medulla (RVM) on the activity of dura-sensitive spinal trigeminal nucleus caudalis (Vc) neurons. Methods Rats were implanted with either morphine or placebo pellets for six to seven days before the microinjection of naloxone methiodide or phosphate-buffered saline into the RVM in urethane-anesthetized animals. Dura-sensitive neurons were recorded in the Vc and the production of c-Fos-like immunoreactivity was quantified. Results In chronic morphine-treated animals, naloxone methiodide microinjections produced a significant increase both in ongoing and facial heat-evoked activity and an increase in Fos-positive neurons in the Vc and in the nucleus reticularis dorsalis, a brainstem region involved in diffuse noxious inhibitory controls. Conclusions These results indicate that activation of pronociceptive neurons in the RVM under conditions of morphine withdrawal can increase the activity of neurons that transmit headache pain. Modulation of the subnucleus reticularis dorsalis by the RVM may explain the attenuation of conditioned pain modulation in patients with chronic headache.
authors.affiliation: 1 Division of Physiology, Kyushu Dental University, Japan.
authors.forename: Suzuro
authors.initials: S
authors.lastname: Hitomi
authors.affiliation: 2 Center for Excellence in the Neurosciences, University of New England, USA.
authors.forename: Konrad
authors.initials: K
authors.lastname: Kross
authors.affiliation: 3 Division of Oral Physiology, Department of Oral Biological Sciences, Niigata University, Graduate School of Medical and Dental Sciences, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kurose
authors.affiliation: 4 Department of Pharmacology, College of Medicine, University of Arizona, Health Sciences Center, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Porreca
authors.affiliation: 2 Center for Excellence in the Neurosciences, University of New England, USA.|5 Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, USA.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Meng
mesh_terms: D000818:Animals; D004343:Drug Implants; D004388:Dura Mater / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D008845:Microinjections / Q000379:methods; D009020:Morphine / Q000008:administration & dosage / Q000009:adverse effects*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*; D014276:Trigeminal Nerve / Q000187:drug effects / Q000378:metabolism*
chemical_list: D004343:Drug Implants; D016760:Proto-Oncogene Proteins c-fos; D009020:Morphine
keywords: Nucleus raphe magnus; medication-overuse headache; opioid; rat; rebound headache