TY - JOUR
T1 - Serotonergic fiber sprouting to external anal sphincter motoneurons after spinal cord contusion
AU - Holmes, Gregory M.
AU - Van Meter, Montina J.
AU - Beattie, Michael S.
AU - Bresnahan, Jacqueline C.
N1 - Funding Information:
This study was supported by NIH research grant NS-31193 and Paralyzed Veterans of America Spinal Cord Research Foundation grant SCRF-1254. The authors wish to thank Dr. Kim Anderson for early access to her ongoing survey of SCI patients, Dr. G.E. Hermann for her comments during the preparation of the manuscript, J.H. Komon Jr. for his expertise and assistance with anatomical analysis and figures, and R. Diebert, C. Forridor, and C.A. Tovar for their technical assistance.
PY - 2005/5
Y1 - 2005/5
N2 - The present study analyzed the anatomical plasticity of serotonergic immunoreactive projections to external anal sphincter (EAS) motoneurons, and the behavioral plasticity of EAS reflexes, penile erection, and locomotion in rats with spinal contusion injury (SCI) or complete spinal cord transection (TX). Electromyographic activity of the EAS, penile erection latency, and BBB locomotor score exhibited parallel recovery over the 6-week recovery period after contusion SCI. This pattern of recovery was not observed in TX animals. While locomotor scores demonstrated a small increase after TX, erectile and anorectal function remained at abnormal levels established immediately after injury. Serotonergic immunofluorescent (5-HT-IF) staining at the lesion site identified a small number of fibers spared after SCI that may provide a substrate for functional recovery. Pixel density measurements of 5-HT-IF in the vicinity of retrogradely labeled EAS and unlabeled pudendal motoneurons necessary for penile erection provide indirect evidence of serotonergic sprouting that parallels the observed functional recovery in animals with SCI. No 5-HT-IF was detected caudal to the injury site in TX animals. These studies indicate: (1) lumbosacral eliminative and reproductive reflexes provide a valid means of studying the mechanisms of post-SCI plasticity; (2) the similar recovery curves suggest similar return of descending control, perhaps through sprouting of descending serotonergic fibers; (3) the observed deficits after TX likely represent the permanent removal of descending inhibition and reflect reorganization of segmental circuitry.
AB - The present study analyzed the anatomical plasticity of serotonergic immunoreactive projections to external anal sphincter (EAS) motoneurons, and the behavioral plasticity of EAS reflexes, penile erection, and locomotion in rats with spinal contusion injury (SCI) or complete spinal cord transection (TX). Electromyographic activity of the EAS, penile erection latency, and BBB locomotor score exhibited parallel recovery over the 6-week recovery period after contusion SCI. This pattern of recovery was not observed in TX animals. While locomotor scores demonstrated a small increase after TX, erectile and anorectal function remained at abnormal levels established immediately after injury. Serotonergic immunofluorescent (5-HT-IF) staining at the lesion site identified a small number of fibers spared after SCI that may provide a substrate for functional recovery. Pixel density measurements of 5-HT-IF in the vicinity of retrogradely labeled EAS and unlabeled pudendal motoneurons necessary for penile erection provide indirect evidence of serotonergic sprouting that parallels the observed functional recovery in animals with SCI. No 5-HT-IF was detected caudal to the injury site in TX animals. These studies indicate: (1) lumbosacral eliminative and reproductive reflexes provide a valid means of studying the mechanisms of post-SCI plasticity; (2) the similar recovery curves suggest similar return of descending control, perhaps through sprouting of descending serotonergic fibers; (3) the observed deficits after TX likely represent the permanent removal of descending inhibition and reflect reorganization of segmental circuitry.
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U2 - 10.1016/j.expneurol.2005.01.002
DO - 10.1016/j.expneurol.2005.01.002
M3 - Article
C2 - 15817262
AN - SCOPUS:16244415846
SN - 0014-4886
VL - 193
SP - 29
EP - 42
JO - Experimental Neurology
JF - Experimental Neurology
IS - 1
ER -