Immediate plasticity in the motor pathways after spinal cord hemisection: implications for transcranial magnetic motor-evoked potentials.
The present study evaluates motor functional recovery after C2 spinal cord hemisection with or without contralateral brachial root transection, which causes a condition that is similar to the crossed phrenic phenomenon on rats. Descending motor pathways, including the reticulospinal extrapyramidal tract and corticospinal pyramidal tracts, were evaluated by transcranial magnetic motor-evoked potentials (mMEPs) and direct cortical electrical motor-evoked potentials (eMEP), respectively. All MEPs recorded from the left forelimb were abolished immediately after the left C2 hemisection. Left mMEPs recovered dramatically immediately after contralateral right brachial root transection. Corticospinal eMEPs never recovered, regardless of transection. The facilitation of mMEPs in animals that had undergone combined contralateral root transection was well correlated with open-field behavioral motor performance. Both electrophysiological and neurological facilitations were significantly attenuated by the selective serotonin synthesis inhibitor para-chlorophenylalanine (p-CPA). These results suggest that serotonergic reticulospinal fibers located contralateral to hemisection contribute to the behavioral and electrophysiological improvement that immediately follows spinal cord injury (SCI).
Fujiki
Minoru
M
Department of Neurosurgery, School of Medicine, Oita University, Hasama-machi, Japan. fujiki@med.oita-u.ac.jp
Kobayashi
Hidenori
H
Inoue
Ryo
R
Ishii
Keisuke
K
D000818:Animals; D004525:Efferent Pathways / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D004558:Electric Stimulation / Q000295:instrumentation / Q000379:methods; D019054:Evoked Potentials, Motor; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D007839:Functional Laterality / Q000502:physiology; D008280:Magnetics; D009333:Neck; D009473:Neuronal Plasticity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000473:pathology / Q000503:physiopathology*; D013126:Spinal Nerve Roots / Q000503:physiopathology / Q000601:surgery
D012702:Serotonin Antagonists; D010134:Fenclonine