Motor learning changes GABAergic terminals on spinal motoneurons in normal rats.
The role of spinal cord plasticity in motor learning is largely unknown. This study explored the effects of H-reflex operant conditioning, a simple model of motor learning, on GABAergic input to spinal motoneurons in rats. Soleus motoneurons were labeled by retrograde transport of a fluorescent tracer and GABAergic terminals on them were identified by glutamic acid decarboxylase (GAD)67 immunoreactivity. Three groups were studied: (i) rats in which down-conditioning had reduced the H-reflex (successful HRdown rats); (ii) rats in which down-conditioning had not reduced the H-reflex (unsuccessful HRdown rats) and (iii) unconditioned (naive) rats. The number, size and GAD density of GABAergic terminals, and their coverage of the motoneuron, were significantly greater in successful HRdown rats than in unsuccessful HRdown or naive rats. It is likely that these differences are due to modifications in terminals from spinal interneurons in lamina VI-VII and that the increased terminal number, size, GAD density and coverage in successful HRdown rats reflect and convey a corticospinal tract influence that changes motoneuron firing threshold and thereby decreases the H-reflex. GABAergic terminals in spinal cord change after spinal cord transection. The present results demonstrate that such spinal cord plasticity also occurs in intact rats in the course of motor learning and suggest that this plasticity contributes to skill acquisition.
Wang
Yu
Y
Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York, PO Box 509, Albany, NY 12201, USA. ywang@wadsworth.org
Pillai
Shreejith
S
Wolpaw
Jonathan R
JR
Chen
Xiang Yang
XY
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D002452:Cell Count; D003216:Conditioning, Operant / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006181:H-Reflex / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D007150:Immunohistochemistry / Q000379:methods; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D017729:Presynaptic Terminals / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D007527:Isoenzymes; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1