Self-reinnervated muscles lose autogenic length feedback, but intermuscular feedback can recover functional connectivity.
In this study, we sought to identify sensory circuitry responsible for motor deficits or compensatory adaptations after peripheral nerve cut and repair. Self-reinnervation of the ankle extensor muscles abolishes the stretch reflex and increases ankle yielding during downslope walking, but it remains unknown whether this finding generalizes to other muscle groups and whether muscles become completely deafferented. In decerebrate cats at least 19 wk after nerve cut and repair, we examined the influence of quadriceps (Q) muscles' self-reinnervation on autogenic length feedback, as well as intermuscular length and force feedback, among the primary extensor muscles in the cat hindlimb. Effects of gastrocnemius and soleus self-reinnervation on intermuscular circuitry were also evaluated. We found that autogenic length feedback was lost after Q self-reinnervation, indicating that loss of the stretch reflex appears to be a generalizable consequence of muscle self-reinnervation. However, intermuscular force and length feedback, evoked from self-reinnervated muscles, was preserved in most of the interactions evaluated with similar relative inhibitory or excitatory magnitudes. These data indicate that intermuscular spinal reflex circuitry has the ability to regain functional connectivity, but the restoration is not absolute. Explanations for the recovery of intermuscular feedback are discussed, based on identified mechanisms responsible for lost autogenic length feedback. Functional implications, due to permanent loss of autogenic length feedback and potential for compensatory adaptations from preserved intermuscular feedback, are discussed.
School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; mlyle@ap.gatech.edu.
Mark A
MA
Lyle
School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia;
Boris I
BI
Prilutsky
School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California; and.
Robert J
RJ
Gregor
School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia; Department of Cell Biology, Emory University, Atlanta, Georgia.
Thomas A
TA
Abelew
School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia;
T Richard
TR
Nichols
D000818:Animals; D000843:Ankle Joint / Q000294:innervation; D002415:Cats; D004195:Disease Models, Animal; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006614:Hindlimb / Q000294:innervation / Q000503:physiopathology; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology* / Q000601:surgery; D059348:Peripheral Nerve Injuries / Q000503:physiopathology* / Q000601:surgery*; D020127:Recovery of Function / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*
Golgi tendon organ; force feedback; muscle self-reinnervation; stretch reflex