Responses of spinal dorsal horn neurons to foot movements in rats with a sprained ankle

Acute ankle injuries are common problems and often lead to persistent pain. To investigate the underlying mechanism of ankle sprain pain, the response properties of spinal dorsal horn neurons were examined after ankle sprain. Acute ankle sprain was induced manually by overextending the ankle of a rat hindlimb in a direction of plantarflexion and inversion. The weight-bearing ratio (WBR) of the affected foot was used as an indicator of pain. Single unit activities of dorsal horn neurons in response to plantarflexion and inversion of the foot or ankle compression were recorded from the medial part of the deep dorsal horn, laminae IV-VI, in normal and ankle-sprained rats. One day after ankle sprain, rats showed significantly reduced WBRs on the affected foot, and this reduction was partially restored by systemic morphine. The majority of deep dorsal horn neurons responded to a single ankle stimulus modality. After ankle sprain, the mean evoked response rates were significantly increased, and afterdischarges were developed in recorded dorsal horn neurons. The ankle sprain-induced enhanced evoked responses were significantly reduced by morphine, which was reversed by naltrexone. The data indicate that movement-specific dorsal horn neuron responses were enhanced after ankle sprain in a morphine-dependent manner, thus suggesting that hyperactivity of dorsal horn neurons is an underlying mechanism of pain after ankle sprain.

Kim, Jae Hyo
Kim, Hee Young
Chung, Kyungsoon
Chung, Jin Mo
Item Type: 
Journal Article
Publication Title: 
Journal of Neurophysiology
Journal Abbreviation: 
J. Neurophysiol.
Publication Date: 
May 2011
Publication Year: 
Library Catalog: 
NCBI Published Medical (?)
PMID: 21389306 PMCID: PMC3094192

Turabian/Chicago Citation

Jae Hyo Kim, Hee Young Kim, Kyungsoon Chung and Jin Mo Chung. May 2011. "Responses of spinal dorsal horn neurons to foot movements in rats with a sprained ankle." Journal of Neurophysiology 105: 5: 2043-2049. 10.1152/jn.00852.2010.

Wikipedia Citation

<ref> {{Cite journal | doi = 10.1152/jn.00852.2010 | issn = 1522-1598 | volume = 105 | pages = 2043-2049 | last = Kim | first = Jae Hyo | coauthors = Kim, Hee Young, Chung, Kyungsoon, Chung, Jin Mo | title = Responses of spinal dorsal horn neurons to foot movements in rats with a sprained ankle | journal = Journal of Neurophysiology | date = May 2011 | pmid = | pmc = }} </ref>