title: Role of thalamic nuclei in the modulation of Fos expression within the cerebral cortex during hypertonic saline-induced muscle nociception.
abstract: It has been proposed that thalamic mediodorsal (MD) and ventromedial (VM) nuclei form thalamic 'nociceptive discriminators' in discrimination of nociceptive afferents, and specifically govern endogenous descending facilitation and inhibition. The present study conducted in rats was to explore the role of thalamic MD and VM nuclei in modulation of cerebral neuronal activities by means of detection of spatiotemporal variations of Fos expression within the cerebral cortex. Following a unilateral intramuscular injection of 5.8% saline into the gastrocnemius muscle, Fos expression within the bilateral, different areas of the cerebral cortex except S2 was significantly increased (P<0.05). Particularly, the increases in Fos expression within the cingulate cortex and the insular cortex occurred at 0.5h, 4h and reached the peak level at 4h, 16h, respectively. Electrolytic lesion of the contralateral thalamic MD and VM nuclei significantly blocked the 5.8% saline intramuscularly induced increases in Fos expression within the bilateral cingulate and insular cortices, respectively. Additionally, the 5.8% saline-induced Fos expression in the cingulate cortex and the insular cortex were dose-dependently attenuated by microinjection of μ-opioid antagonist β-funaltrexamine hydrochloride into the thalamic MD and VM nuclei. It is suggested that (1) the neural circuits of 'thalamic MD nucleus - cingulate cortex' and 'thalamic VM nucleus - insular cortex' form two distinct pathways in the endogenous control of nociception, (2) mirror or contralateral pain is hypothesized to be related to cross-talk of neuronal activities within the bilateral cerebral cortices modulated by μ-opioid receptors within the thalamic MD and VM nuclei.
authors.affiliation: Center for Biomedical Research on Pain (CBRP), College of Medicine, Xi'an Jiaotong University, Xi'an 710061, PR China; Department of Anesthesiology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, PR China.
authors.forename: Y
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Center for Biomedical Research on Pain (CBRP), College of Medicine, Xi'an Jiaotong University, Xi'an 710061, PR China.
authors.forename: J
authors.initials: J
authors.lastname: Lei
authors.affiliation: Department of Pain, Tongji Hospital Affiliated to Shanghai Tongji University, Shanghai 200065, PR China.
authors.forename: G
authors.initials: G
authors.lastname: Ye
authors.affiliation: Institute of Neurosciences, The Fourth Military Medical University, Xi'an 710032, PR China.
authors.forename: H
authors.initials: H
authors.lastname: Xu
authors.affiliation: Center for Biomedical Research on Pain (CBRP), College of Medicine, Xi'an Jiaotong University, Xi'an 710061, PR China. Electronic address: yhj@mail.xjtu.edu.cn.
authors.forename: H-J
authors.initials: HJ
authors.lastname: You
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D007839:Functional Laterality / Q000502:physiology; D008297:Male; D063806:Myalgia / Q000188:drug therapy / Q000378:metabolism*; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives; D009292:Narcotic Antagonists / Q000008:administration & dosage; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D059226:Nociceptive Pain / Q000188:drug therapy / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000378:metabolism; D012462:Saline Solution, Hypertonic; D013787:Thalamic Nuclei / Q000187:drug effects / Q000293:injuries / Q000378:metabolism*; D013997:Time Factors
chemical_list: D009292:Narcotic Antagonists; D016760:Proto-Oncogene Proteins c-fos; D017450:Receptors, Opioid, mu; D012462:Saline Solution, Hypertonic; D009271:Naltrexone; C024524:beta-funaltrexamine
keywords: Fos expression; cerebral cortex; endogenous controls; mirror pain; μ-opioid receptor