کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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3057306 | 1186594 | 2007 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Up-regulation of 5-HT2 receptors is involved in the increased H-reflex amplitude after contusive spinal cord injury Up-regulation of 5-HT2 receptors is involved in the increased H-reflex amplitude after contusive spinal cord injury](/preview/png/3057306.png)
The amplitude of the H-reflex increases chronically after incomplete SCI and is associated with the development of exaggerated hindlimb reflexes. Although the mechanism for this increased H-reflex is not clear, previous studies have shown that pharmacological activation of the 5-HT2 receptors (5-HT2R) can potentiate the monosynaptic reflex. This study tested the hypothesis that increased expression of 5-HT2R on motoneurons is involved in increased H-reflex amplitude after a standardized clinically relevant contusive SCI. Adult female rats were subjected to contusion, complete surgical transection, or a T8 laminectomy only. At 4 weeks after surgery, H-reflex recordings from the hindpaw plantar muscles of contused rats showed twice the amplitude of that in laminectomy controls or transected rats. To probe the role of 5-HT2R in this increased amplitude, dose–response studies were done with the selective antagonists mianserin or LY53857 and the 5-HT2R agonist (±)-1-(2,5-Dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI). The drugs were intrathecally infused into the lumbar cord while recording the H-reflex. Mianserin did not have any significant effects on the H-reflex after transection, consistent with the loss of distal serotonergic innervation. After contusion, both 5-HT2R antagonists reduced the H-reflex reflex amplitude with a significantly higher ID50 compared to the uninjured controls. The 5-HT2R agonist DOI significantly increased reflex amplitude in contused but not control rats. Furthermore, while 5-HT immunoreactivity was similar, contused rats displayed increased 5-HT2AR immunoreactivity in plantar muscle motoneurons compared to uninjured controls. We conclude that increased expression of 5-HT2R is likely to be involved in the enhanced H-reflex that develops after contusive SCI.
Journal: Experimental Neurology - Volume 203, Issue 2, February 2007, Pages 502–511