title: Enhanced Gamma Oscillatory Activity in Rats with Chronic Inflammatory Pain.
abstract: It has been reported that oscillatory gamma activity participates in brief acute pain and tonic ongoing pain. It is of great interest to determine whether the gamma activity is involved in chronic pain since chronic pain is a more severe pathological condition characterized by pain persistency. To investigate the oscillatory gamma activity in chronic pain, in the present study, we recorded spontaneous electrocorticogram (ECoG) signals during chronic pain development in rats with chronic inflammatory pain induced by monoarthritis. Power spectrum analysis of ECoG data showed that gamma power increased significantly at the late stage of chronic inflammatory pain. The increased gamma activity occurred mainly at electrodes over primary somatosensory cortices. In rats with chronic pain, the gamma power was positively correlated with the hyperalgesia measured by laser energy that elicited hindpaw withdrawal response. Furthermore, an increased coupling between the amplitude of gamma power and the phase of theta oscillations was observed in chronic inflammatory pain condition. These results indicate an enhanced spontaneous gamma activity in chronic pain and suggest a potential biomarker for the severity of chronic pain.
authors.affiliation: Department of Neurobiology, School of Basic Medical Sciences/Beijing Institute for Brain Disorders, Capital Medical University Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Neuroscience Research Institute, Peking UniversityBeijing, China; Peking University Sixth Hospital/National Clinical Research Center for Mental Disorders, Key Laboratory of Mental Health, Ministry of Health (Peking University)Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Neuroscience Research Institute, Peking University Beijing, China.
authors.forename: Guo-Gang
authors.initials: GG
authors.lastname: Xing
authors.affiliation: State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University Beijing, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Li
authors.affiliation: Neuroscience Research Institute, Peking UniversityBeijing, China; Key Laboratory for Neuroscience, Ministry of Education/National Health and Family Planning Commission, Peking UniversityBeijing, China.
authors.forename: You
authors.initials: Y
authors.lastname: Wan
keywords: chronic pain; cross-frequency coupling; gamma activity; hyperalgesia; inflammatory pain; rat; spontaneous electrocorticogram